Last visit was: 02 Sep 2026, 09:13 It is currently 02 Sep 2026, 09:13
Home
Messages
Tests
Schools
Events
Close
GMAT Club Daily Prep
Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
Go to My Error Log Learn more
Close
Request Expert Reply
Confirm Cancel
Back to Forum
Create Topic
805+ (Hard)|   Bold Face CR|      
User avatar
ashutosh_73
User avatar
Joined: 19 Jan 2018
Last visit: 30 Oct 2024
Posts: 216
Own Kudos:
2,182
 [62]
Given Kudos: 86
Location: India
Posts: 216
Kudos: 2,182
 [62]
­Under laboratory conditions, fruit flies can learn to respond 08 Mar 2024, 08:32
2
Kudos
Add Kudos
60
Bookmarks
Bookmark this Post
00:00
Start Timer
Pause Timer
Resume Timer
Show Answer
Hide
Show
History
D
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!

Difficulty:

95% (hard)

Question Stats:

50% (02:44) correct 50% (02:48) wrong based on 826 sessions

History

Date
Time
Result
Not Attempted Yet
­Under laboratory conditions, fruit flies can learn to respond to odors that elicit no response from them in nature. Mutant fruit flies that cannot produce a certain enzyme are, however, incapable of such learning. These mutant flies respond to other odors just as ordinary fruit flies do. Thus it is unlikely that the enzyme's absence impairs the fruit flies' perception of odors, since presumably fruit flies would not have an enzyme that was needed only for the perception of odors that fruit flies do not respond to in nature. Given that many researchers believe that this enzyme is somehow involved in the process of forming memories, what the enzyme's absence probably impairs is the fruit flies' ability to learn.

In the argument given, the two boldfaced portions play which of the following roles?

A) The first is an explanatory hypothesis provisionally put forward in the argument; the second provides evidence in support of that hypothesis.
B) The first is evidence that has been used to support a hypothesis that the argument challenges; the second states an assumption explicitly made in challenging that hypothesis.
C) The first is evidence that has been used to support a hypothesis that the argument challenges; the second is a modified version of that hypothesis that is adopted in the argument.
D) The first is evidence used in ruling out a potential explanation that the argument rejects; the second presents an explicit assumption used in arguing against that explanation.
E) The first is evidence used in ruling out a potential explanation that the argument rejects; the second is the explanatory hypothesis that the argument as a whole seeks to support.­
ShowHide Answer
Official Answer
D
Need more Tests to Practice? GMAT Club Tests give expert solutions for every question in full and sectional GMAT Focus mocks. Learn more →
Most Helpful Reply
User avatar
gmatophobia
User avatar
Quant Chat Moderator
Joined: 22 Dec 2016
Last visit: 30 Aug 2026
Posts: 3,174
Own Kudos:
12,302
 [6]
Given Kudos: 1,860
Location: India
Concentration: Strategy, Leadership
Posts: 3,174
Kudos: 12,302
 [6]
­Under laboratory conditions, fruit flies can learn to respond 09 Mar 2024, 01:19
4
Kudos
Add Kudos
2
Bookmarks
Bookmark this Post
 
ashutosh_73
­Under laboratory conditions, fruit flies can learn to respond to odors that elicit no response from them in nature. Mutant fruit flies that cannot produce a certain enzyme are, however, incapable of such learning. These mutant flies respond to other odors just as ordinary fruit flies do. Thus it is unlikely that the enzyme's absence impairs the fruit flies' perception of odors, since presumably fruit flies would not have an enzyme that was needed only for the perception of odors that fruit flies do not respond to in nature. Given that many researchers believe that this enzyme is somehow involved in the process of forming memories, what the enzyme's absence probably impairs is the fruit flies' ability to learn.
In the argument given, the two boldfaced portions play which of the following roles?
A) The first is an explanatory hypothesis provisionally put forward in the argument; the second provides evidence in support of that hypothesis.
B) The first is evidence that has been used to support a hypothesis that the argument challenges; the second states an assumption explicitly made in challenging that hypothesis.
C) The first is evidence that has been used to support a hypothesis that the argument challenges; the second is a modified version of that hypothesis that is adopted in the argument.
D) The first is evidence used in ruling out a potential explanation that the argument rejects; the second presents an explicit assumption used in arguing against that explanation.
E) The first is evidence used in ruling out a potential explanation that the argument rejects; the second is the explanatory hypothesis that the argument as a whole seeks to support.­
Show more
­This is a tricky one and a lot is going on in this passage. Let's try to break down the passage.
­Under laboratory conditions, fruit flies can learn to respond to odors that elicit no response from them in nature. → A fact is presented, hence, this statement is a premise of the argument. 
Mutant fruit flies that cannot produce a certain enzyme are, however, incapable of such learning. → A fact is presented, hence, this statement is a premise of the argument. 
These mutant flies respond to other odors just as ordinary fruit flies do. → A fact is presented, hence, this statement is a premise of the argument. 
Thus it is unlikely that the enzyme's absence impairs the fruit flies' perception of odors → The author concludes that "it is unlikely that the enzyme's absence impairs the fruit flies' perception of odors ". This statement is a conclusion. We don't know if this is an intermediatory conclusion or the main conclusion of the argument. So let's keep reading. 
since presumably fruit flies would not have an enzyme that was needed only for the perception of odors that fruit flies do not respond to in nature. → Since is a premise marker. The statement provides some facts/reasons to support the conclusion. The word "presumably" indicates that the author is assuming the details. 
Given that many researchers believe that this enzyme is somehow involved in the process of forming memories, → The author provides evidence to support his claim. 
what the enzyme's absence probably impairs is the fruit flies' ability to learn → This part is again a conclusion and is the views of the author. 
Out of the two conclusions above "Thus it is unlikely that the enzyme's absence impairs the fruit flies' perception of odors" is the main conclusion of the argument. 
Answer Choice Elimination
A) The first is an explanatory hypothesis provisionally put forward in the argument; the second provides evidence in support of that hypothesis.
The first part of this option is incorrect. The first bold fact doesn't explain anything but is merely a fact presented by the author. Hence, eliminate A. 
B) The first is evidence that has been used to support a hypothesis that the argument challenges; the second states an assumption explicitly made in challenging that hypothesis.
The first boldface, "These mutant flies respond to other odors just as ordinary fruit flies do", does serve as evidence to support a hypothesis, "it is unlikely that the enzyme's absence impairs the fruit flies' perception of odors" that the argument challenges. This is correct because the author does share his viewpoints in the second conclusion. He states "the enzyme's absence probably impairs the fruit flies' ability to learn". So he believes that the absence of the enzymes doesn't impair the files' perception of odors but impairs its perception of learning.
The second part of the option is incorrect. The second boldface doesn't challenge the hypothesis but supports the hypothesis of the author. 
C) The first is evidence that has been used to support a hypothesis that the argument challenges; the second is a modified version of that hypothesis that is adopted in the argument.
The first boldface, "These mutant flies respond to other odors just as ordinary fruit flies do", does serve as evidence to support a hypothesis, "it is unlikely that the enzyme's absence impairs the fruit flies' perception of odors" that the argument challenges. This is correct because the author does share his viewpoints in the second conclusion. He states "the enzyme's absence probably impairs the fruit flies' ability to learn". So he believes that the absence of the enzymes doesn't impair the files' perception of odors but impairs its perception of learning.
The second bold face is not a modified version of the hypothesis but an assumption that's used to support the hypothesis. Hence, this option is incorrect. 
D) The first is evidence used in ruling out a potential explanation that the argument rejects; the second presents an explicit assumption used in arguing against that explanation.
The first part of the boldface is correct. The first boldface, "These mutant flies respond to other odors just as ordinary fruit flies do", is used to rule out a potential explanation, "that the enzyme's absence impairs the fruit flies' perception of odors", and the argument also rejects this explanation. 
The second boldface is also correct. It presents an assumption that the author has made while concluding. The author assumes that fruit flies would not have an enzyme that was needed only for the perception of odors that fruit flies do not respond to in nature. Also, the author challenges the explanation "that the enzyme's absence impairs the fruit flies' perception of odors". Hence, both parts are correct. Let's keep. 
E) The first is evidence used in ruling out a potential explanation that the argument rejects; the second is the explanatory hypothesis that the argument as a whole seeks to support.­
The first part of the boldface is correct. The first boldface, "These mutant flies respond to other odors just as ordinary fruit flies do", is used to rule out a potential explanation, "that the enzyme's absence impairs the fruit flies' perception of odors", and the argument also rejects this explanation. 
The second part of this option is incorrect. The second boldface is an assumption that's made while concluding. It's not doesn't explain anything. We can eliminate E. ­
Option D
General Discussion
User avatar
Gemmie
User avatar
Joined: 19 Dec 2021
Last visit: 27 Apr 2026
Posts: 480
Own Kudos:
522
 [4]
Given Kudos: 76
Location: Viet Nam
Concentration: Technology, Economics
GMAT Focus 1: 695 Q87 V84 DI83
GPA: 3.55
GMAT Focus 1: 695 Q87 V84 DI83
Posts: 480
Kudos: 522
 [4]
­Under laboratory conditions, fruit flies can learn to respond 07 Jun 2024, 23:39
4
Kudos
Add Kudos
Bookmarks
Bookmark this Post
­The argument is trying to show that the enzyme is involved in learning, not perception.

These mutant flies respond to other odors just as ordinary fruit flies do. Thus it is unlikely that the enzyme's absence impairs the fruit flies' perception of odors, since presumably fruit flies would not have an enzyme that was needed only for the perception of odors that fruit flies do not respond to in nature.

Both bold parts support the central argument that the enzyme is not involved in perception.

1. The first bold part
- is an evidence => rule out A
- supports the argument => rule out B and C

D and E identify the same about the first bold part. 

The first is evidence used in ruling out a potential explanation that the argument rejects

==> What is the mentioned explanation: 
+ the explanation is for why Under laboratory conditions, fruit flies can learn to respond to odors that elicit no response from them in nature. Mutant fruit flies that cannot produce a certain enzyme are, however, incapable of such learning 
+ the explanation says that enzyme's absence impairs the fruit flies' perception of odors

==> The argument rejects this explanation and says that the enzyme interfere with the learning ability

2. The second bold part

E suggests the argument supports the hypothesis mentioned in second bold part. However, it is the 2nd is rather an assumption based on which the argument (i.e. arguing against the explanation) is made, which is D

 ­
User avatar
siddd30
User avatar
Joined: 02 Sep 2020
Last visit: 18 Jan 2025
Posts: 17
Own Kudos:
15
 [3]
Given Kudos: 27
GMAT Focus 1: 715 Q87 V88 DI81
Products:
My Reviews
GMAT Focus 1: 715 Q87 V88 DI81
Posts: 17
Kudos: 15
 [3]
­Under laboratory conditions, fruit flies can learn to respond 05 Jul 2024, 00:14
3
Kudos
Add Kudos
Bookmarks
Bookmark this Post
gmatophobia

ashutosh_73
­Under laboratory conditions, fruit flies can learn to respond to odors that elicit no response from them in nature. Mutant fruit flies that cannot produce a certain enzyme are, however, incapable of such learning. These mutant flies respond to other odors just as ordinary fruit flies do. Thus it is unlikely that the enzyme's absence impairs the fruit flies' perception of odors, since presumably fruit flies would not have an enzyme that was needed only for the perception of odors that fruit flies do not respond to in nature. Given that many researchers believe that this enzyme is somehow involved in the process of forming memories, what the enzyme's absence probably impairs is the fruit flies' ability to learn.
In the argument given, the two boldfaced portions play which of the following roles?
A) The first is an explanatory hypothesis provisionally put forward in the argument; the second provides evidence in support of that hypothesis.
B) The first is evidence that has been used to support a hypothesis that the argument challenges; the second states an assumption explicitly made in challenging that hypothesis.
C) The first is evidence that has been used to support a hypothesis that the argument challenges; the second is a modified version of that hypothesis that is adopted in the argument.
D) The first is evidence used in ruling out a potential explanation that the argument rejects; the second presents an explicit assumption used in arguing against that explanation.
E) The first is evidence used in ruling out a potential explanation that the argument rejects; the second is the explanatory hypothesis that the argument as a whole seeks to support.­
­This is a tricky one and a lot is going on in this passage. Let's try to break down the passage.
­Under laboratory conditions, fruit flies can learn to respond to odors that elicit no response from them in nature. → A fact is presented, hence, this statement is a premise of the argument. 
Mutant fruit flies that cannot produce a certain enzyme are, however, incapable of such learning. → A fact is presented, hence, this statement is a premise of the argument. 
These mutant flies respond to other odors just as ordinary fruit flies do. → A fact is presented, hence, this statement is a premise of the argument. 
Thus it is unlikely that the enzyme's absence impairs the fruit flies' perception of odors → The author concludes that "it is unlikely that the enzyme's absence impairs the fruit flies' perception of odors ". This statement is a conclusion. We don't know if this is an intermediatory conclusion or the main conclusion of the argument. So let's keep reading. 
since presumably fruit flies would not have an enzyme that was needed only for the perception of odors that fruit flies do not respond to in nature. → Since is a premise marker. The statement provides some facts/reasons to support the conclusion. The word "presumably" indicates that the author is assuming the details. 
Given that many researchers believe that this enzyme is somehow involved in the process of forming memories, → The author provides evidence to support his claim. 
what the enzyme's absence probably impairs is the fruit flies' ability to learn → This part is again a conclusion and is the views of the author. 
Out of the two conclusions above "Thus it is unlikely that the enzyme's absence impairs the fruit flies' perception of odors" is the main conclusion of the argument. 
Answer Choice Elimination
A) The first is an explanatory hypothesis provisionally put forward in the argument; the second provides evidence in support of that hypothesis.
The first part of this option is incorrect. The first bold fact doesn't explain anything but is merely a fact presented by the author. Hence, eliminate A. 
B) The first is evidence that has been used to support a hypothesis that the argument challenges; the second states an assumption explicitly made in challenging that hypothesis.
The first boldface, "These mutant flies respond to other odors just as ordinary fruit flies do", does serve as evidence to support a hypothesis, "it is unlikely that the enzyme's absence impairs the fruit flies' perception of odors" that the argument challenges. This is correct because the author does share his viewpoints in the second conclusion. He states "the enzyme's absence probably impairs the fruit flies' ability to learn". So he believes that the absence of the enzymes doesn't impair the files' perception of odors but impairs its perception of learning.
The second part of the option is incorrect. The second boldface doesn't challenge the hypothesis but supports the hypothesis of the author. 
C) The first is evidence that has been used to support a hypothesis that the argument challenges; the second is a modified version of that hypothesis that is adopted in the argument.
The first boldface, "These mutant flies respond to other odors just as ordinary fruit flies do", does serve as evidence to support a hypothesis, "it is unlikely that the enzyme's absence impairs the fruit flies' perception of odors" that the argument challenges. This is correct because the author does share his viewpoints in the second conclusion. He states "the enzyme's absence probably impairs the fruit flies' ability to learn". So he believes that the absence of the enzymes doesn't impair the files' perception of odors but impairs its perception of learning.
The second bold face is not a modified version of the hypothesis but an assumption that's used to support the hypothesis. Hence, this option is incorrect. 
D) The first is evidence used in ruling out a potential explanation that the argument rejects; the second presents an explicit assumption used in arguing against that explanation.
The first part of the boldface is correct. The first boldface, "These mutant flies respond to other odors just as ordinary fruit flies do", is used to rule out a potential explanation, "that the enzyme's absence impairs the fruit flies' perception of odors", and the argument also rejects this explanation. 
The second boldface is also correct. It presents an assumption that the author has made while concluding. The author assumes that fruit flies would not have an enzyme that was needed only for the perception of odors that fruit flies do not respond to in nature. Also, the author challenges the explanation "that the enzyme's absence impairs the fruit flies' perception of odors". Hence, both parts are correct. Let's keep. 
E) The first is evidence used in ruling out a potential explanation that the argument rejects; the second is the explanatory hypothesis that the argument as a whole seeks to support.­
The first part of the boldface is correct. The first boldface, "These mutant flies respond to other odors just as ordinary fruit flies do", is used to rule out a potential explanation, "that the enzyme's absence impairs the fruit flies' perception of odors", and the argument also rejects this explanation. 
The second part of this option is incorrect. The second boldface is an assumption that's made while concluding. It's not doesn't explain anything. We can eliminate E. ­
Option D
Show more
­Hey, 

I disagree with the claim wrt the first portion of option b and c, the first is evidence which is used to challenge (and not support) the hypothesis that the argument challenges, IMO.

Hypothesis that the argument challenges- "Enzyme's absence impairs the fruit flies' perception of odors"; so the fact that they can respond to other odors, just as ordinary fruit flies do- suggests that it isnt supporting a hypothesis that the argument challenges
User avatar
Raman109
User avatar
Joined: 17 Aug 2009
Last visit: 28 Jul 2025
Posts: 691
Own Kudos:
230
Given Kudos: 33
Posts: 691
Kudos: 230
­Under laboratory conditions, fruit flies can learn to respond 27 Jul 2024, 08:45
Kudos
Add Kudos
Bookmarks
Bookmark this Post
­Under laboratory conditions, fruit flies can learn to respond to odors that elicit no response from them in nature. - Background info. Fruit Flies (FF) can learn to respond to some odors that FF doesn't typically respond to in nature.

Mutant fruit flies that cannot produce a certain enzyme are, however, incapable of such learning. - Highlights an exception - MFF that can't produce enzyme X and is incapable of learning. Are these correlated? Is enzyme the reason for the lack of learning? We don't know.

These mutant flies respond to other odors just as ordinary fruit flies do. - Another complexity: the MFF responds to other odors. For example, dog type B doesn't respond to the car horns and has different genes than dog A. But that dog B responds to other sounds such as home ring, etc. Its going towards that possibly both are not related in terms of one causing the other.

Thus it is unlikely that the enzyme's absence impairs the fruit flies' perception of odors, since presumably fruit flies would not have an enzyme that was needed only for the perception of odors that fruit flies do not respond to in nature. - exactly. The enzyme can't be the reason/cause of lack of perception or response.

Given that many researchers believe that this enzyme is somehow involved in the process of forming memories, what the enzyme's absence probably impairs is the fruit flies' ability to learn. - opposite to the earlier statement, it means that the enzyme's absence is responsible in some form. How? Without this enzyme, they may still sense it but cant learn as this enzyme is responsible for forming memory.

In the argument given, the two boldfaced portions play which of the following roles?

A) The first is an explanatory hypothesis provisionally put forward in the argument (No, it just states another complexity/fact); the second provides evidence in support of that hypothesis (The 2nd BF is not in support of BF1. The 2nd is an assumption supporting the intermediate conclusion).

B) The first is evidence that has been used to support a hypothesis that the argument challenges (ok); the second states an assumption explicitly made in challenging that hypothesis. (No. It supports the hypothesis that "it is unlikely that the enzyme's absence impairs the fruit flies' perception of odors."

C) The first is evidence that has been used to support a hypothesis that the argument challenges (ok); the second is a modified version of that hypothesis that is adopted in the argument. - No. What is adopted in the argument is that enzymes are somehow responsible - not in perception but in learning.

D) The first is evidence (okay) used in ruling out a potential explanation (what explanation—that the enzyme is required for perception—the idea that the enzyme is important) that the argument rejects (the argument concludes that yes, the enzyme is not required for perception but is required for learning); the second presents an explicit assumption (ok) used in arguing against that explanation(yes the explanation that the enzyme is required for perception—the idea that the enzyme is important ).

E) The first is evidence used in ruling out a potential explanation that the argument rejects (ok); the second is the explanatory hypothesis that the argument as a whole seeks to support. (No, the conclusion doesn't support this)­
User avatar
Goldenfuture
User avatar
Joined: 24 Dec 2024
Last visit: 29 Jan 2026
Posts: 147
Own Kudos:
25
Given Kudos: 48
Posts: 147
Kudos: 25
­Under laboratory conditions, fruit flies can learn to respond 10 Jan 2026, 22:14
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Under laboratory conditions, fruit flies can learn to respond to odors that elicit no response from them in nature. Mutant fruit flies that cannot produce a certain enzyme are, however, incapable of such learning.
BF1 – observation/ premise/ evidence These mutant flies respond to other odors just as ordinary fruit flies do.
Conclusion: Thus it is unlikely that the enzyme's absence impairs the fruit flies' perception of odors,

since presumably fruit flies would not have an enzyme that was needed only for the perception of odors that fruit flies do not respond to in nature. – Explanation/ analysis thinking/ IC

Given that many researchers believe that this enzyme is somehow involved in the process of forming memories, what the enzyme's absence probably impairs is the fruit flies' ability to learn – Main conclusion.


In the argument given, the two boldfaced portions play which of the following roles?

A) The first is an explanatory hypothesis provisionally put forward in the argument; the second provides evidence in support of that hypothesis. – First not hypothesis- eliminate

B) The first is evidence that has been used to support a hypothesis that the argument challenges; the second states an assumption explicitly made in challenging that hypothesis. Point of failure highlighted

C) The first is evidence that has been used to support a hypothesis that the argument challenges; the second is a modified version of that hypothesis that is adopted in the argument. Point of failure highlighted

D) The first is evidence used in ruling out a potential explanation that the argument rejects; the second presents an explicit assumption used in arguing against that explanation - Keep
.
E) The first is evidence used in ruling out a potential explanation that the argument rejects; the second is the explanatory hypothesis that the argument as a whole seeks to support – Conclusion is built on BF2 not support it
Moderators:
GMATNinja
GMAT Club Verbal Expert
7399 posts
AbhishekP220108
Verbal Forum Moderator
705 posts