12 Days of Christmas GMAT Competition - Day 3: Bitter crab disease is

Question

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Bitter crab disease is a parasitic infection that poses a significant danger to crustacean fisheries, since infected crabs  were observed to have increased mortality rates  as high as 86 percent.

(A) were observed to have increased mortality rates
(B) were observed to have increasing mortality rates
(C) have been observed to have increased mortality rates
(D) had been observed to have increased mortality rates
(E) have been observed to have increasing mortality rates

Bunuel · Accepted Answer

Experts' Global Official Explanation:

Tenses + Meaning + Modifiers + Verb Forms

Understanding the intended meaning is key to solving this question; the intended meaning of the crucial part of this sentence is that the mortality rates have been observed to have increased as high as 86 percent.

• The present perfect continuous tense (marked by “has/have been”) is used to refer to actions that started in past and continue into the present. 
• The past perfect continuous tense (marked by the use of helping verb "had/have been") is used when a sentence contains two actions in the past and one action is in the greater past as well as continuous in nature; the helping verb "had been" is used with the action that is in the greater past and continuous in nature.
• The simple past tense is used to refer to actions that concluded in the past.

A. Trap. This answer choice incorrectly uses the simple past tense verb “were observed” to refer to an action that began in the past and continues into the present; please remember, the present perfect continuous tense (marked by “has/have been”) is the correct tense to refer to actions that started in past and continue into the present, and the simple past tense is only used to refer to actions that concluded in the past.

B. This answer choice alters the meaning of the sentence through the phrase “increasing mortality rates”; the use of the present participle (“verb+ing” - “increasing” in this sentence) incorrectly implies that the mortality rates of the crabs are currently increasing and are currently as high as 86 percent; the intended meaning is that the mortality rates   have increased   to be as high as 86 percent. Further, Option B incorrectly uses the simple past tense verb “were observed” to refer to an action that began in the past and continues into the present; please remember, the present perfect continuous tense (marked by has/have been) is the correct tense to refer to actions that started in the past and continue into the present, and the simple past tense is only used to refer to actions that concluded in the past.

C. Correct.  This answer choice correctly uses the present perfect continuous tense verb “have been observed” to refer to an action that began in the past and continues into the present. Further, Option C uses the phrase “increased mortality rates”; the use of the past participle (“increased” in this sentence) conveys the intended meaning- that the mortality rates have been observed to have increased as high as 86 percent.

D. This answer choice incorrectly uses the past perfect continuous tense verb “had been observed” to refer to an action that began in the past and continues into the present; please remember, the present perfect continuous tense (marked by has/have been) is the correct tense to refer to actions that started in the past and continue into the present, and the past perfect continuous tense (marked by the use of helping verb "had/have been") is used when a sentence contains two actions in the past and one action is in the greater past as well as continuous in nature; the helping verb "had been" is used with the action that is in the greater past and continuous in nature.

E. Trap. This answer choice alters the meaning of the sentence through the phrase “increasing mortality rates”; the use of the present participle (“verb+ing” - “increasing” in this sentence) incorrectly implies that the mortality rates of the crabs are currently increasing and are currently as high as 86 percent; the intended meaning is that the mortality rates   have increased   to be as high as 86 percent.

C is the best answer choice.

____________________________
  Video Explanation:

https://www.youtube.com/watch?v=XYFdZrfgwXA

sj296 · Answer

As the Main clause is a generalization that is in the present tense, the subordinate clause also has to be in present tense.

Therefore, A, B, and D are out. Between C and E, C is more appropriate as E uses 'increasing mortality' which changes the meaning that it's still happening.

So, OA should be C

(A)  were  observed to have increased mortality rates
(B)  were  observed to have increasing mortality rates
(C)  have been observed to have increased mortality rates 
(D)  had been  observed to have increased mortality rates
(E) have been observed to have  increasing  mortality rates

nivivacious · Answer

(A) Incorrect : This option states that the reason was in the past but is no longer the case right now
(B) Incorrect: The past tense along with 'increasing" is wrong
 (C) Correct - This indicates that this happened in the past and is still occurring (Present perfect) and the 'increased' here is correct. Our marker 'Since' also agrees with this 
(D) Incorrect: This suggests that the observation was made and completed in the past before another past event (Past perfect) which is incorrect here
(E) Incorrect: While present perfect is correct here, 'increasing' here is wrong.

Hence C

Schinchan_bh · Answer

The correct option for sentence correction is:

(C) have been observed to have increased mortality rates

So the corrected sentence would be: "Bitter crab disease is a parasitic infection that poses a significant danger to crustacean fisheries, as infected crabs have been observed to have increased mortality rates as high as 86 percent."

Archit3110 · Answer

2/3 split
increased vs increasing
increased is correct
eliminate option B & E

(A) were observed to have increased mortality rates  were usage is incorrect.. 
 (C) have been observed to have increased mortality rates  tense issue with usage of have been .. 
 (D) had been observed to have increased mortality rates  correct option

OPTION D is correct

missionmba2025 · Answer

(A)  were  observed to have increased mortality rates

The use of past tense is incorrect here. Were indicates that the mortality rates are no longer applicable.

(B)  were  observed to have increasing mortality rates

The use of past tense is incorrect here. Were indicates that the mortality rates are no longer applicable.

(C) have been observed to have increased mortality rates

The use if present perfect tense is correct here. This option is correct.

(D)  had been  observed to have increased mortality rates

The use of past perfect tense is incorrect here.

(E) have been observed to have  increasing  mortality rates

We should use increased. The use of present continuous tense is not warranted.

IMO C

vishal_gupta · Answer

(A) were observed to have increased mortality rates (Use of past tense 'were' is not correct)
(B) were observed to have increasing mortality rates (Same as A) 
 (C) have been observed to have increased mortality rates (Correct. In comparison to E, increased is better than increasing as observation have been observed to convey some result.) 
 (D) had been observed to have increased mortality rates (Use of past tense 'had been' is incorrect)
(E) have been observed to have increasing mortality rates (Explained in C)

arkanilchaki1204 · Answer

C is the correct choice as this sentence requires present perfect tense

poojaarora1818 · Answer

Bitter crab disease is a parasitic infection that poses a significant danger to crustacean fisheries, since infected crabs  were observed to have increased mortality rates  as high as 86 percent.

(A) were observed to have increased mortality rates Incorrect 
(B) were observed to have increasing mortality rates Incorrect 
(C) have been observed to have increased mortality rates Correct 
(D) had been observed to have increased mortality rates Incorrect 
(E) have been observed to have increasing mortality rates Incorrect

pooh.2304 · Answer

Options (A) and (D) use the past tense "were observed," which suggests a completed action in the past but may not convey the ongoing relevance of the observation to the present situation. Option (B) with "were observed to have increasing mortality rates" is grammatically awkward and less precise in conveying the idea. Option (E) with "have been observed to have increasing mortality rates" also sounds awkward and doesn't convey the intended meaning as clearly as option (C).

SnorLax_7 · Answer

c, d and E are gone due to wrong tense usage.
b/w option A and B, increasing is more suited than increased (may be acting as verb). hence B.

KeithJohnson · Answer

the main clause is in the present tense, so in were/have/had split, we use Have 
rule out A,B, D

between C and E, increased makes more sense than increasing (as we are talking about absolute value 86% here)
C is correct

DongTan · Answer

The correct answer is (C) "have been observed to have increased mortality rates."

The sentence describes a past observation of infected crabs and their increased mortality rates. The use of the present perfect tense "have been observed" correctly indicates that the observation has occurred in the past and has ongoing relevance to the present. Additionally, the phrase "increased mortality rates" accurately conveys the idea that the mortality rates have risen compared to normal levels.

Options (A), (B), and (E) are incorrect because they either use the wrong verb tense or the wrong form of the verb "increase." 
Option (D) is incorrect because it suggests a past action that occurred before another past action, which is not necessary in this context.

Mukulkumar19 · Answer

(A) were observed to have increased mortality rates   incorrect tense 
 (B) were observed to have increasing mortality rates   mismatch tense 
 (C) have been observed to have increased mortality rates    correct use of tense 
 (D) had been observed to have increased mortality rates   had been ??? incorrect tense 
 (E) have been observed to have increasing mortality rates   again mismatch tense

bv8562 · Answer

IMO (C) have been observed to have increased mortality rates

Kinshook · Answer

Bitter crab disease is a parasitic infection 
that poses a significant danger to crustacean fisheries, 
since infected crabs  were observed to have increased mortality rates  as high as 86 percent.

Usage of past tense  were observed  is incorrect

Usage of past tense  were observed  is incorrect
Usage of  increased mortality rates  is better than  increasing mortality rates 
Incorrect

Correct in tense, concise and correct

Usage of past perfect tense  had been  is incorrect

Usage of  increased mortality rates  is better than  increasing mortality rates 
Incorrect

IMO C

Suboopc · Answer

A) 'were' is the incorrect tense. It makes it seem that it was once observed in the past that the mortality rate was high. One cannot present the previous claim based on a one off instance.
B) Same issue as A. 'increasing' makes it seem like 86 percent is  increasing  mortality rates whereas it is the  increased  mortality rate
 C)  This correctly uses 'have been' to show that this is an observed trend which led to the statement earlier.
D) This conveys that the observation has already concluded in the past. If it were only the case in the past, then we cannot make the previous claim.
E) Same issue with 'increasing' as B.

jaysea · Answer

(A) were observed to have increased mortality rates - were here suggests the higher mortality rates are in the past, while the bitter crab disease is being talked about in present tense. wrong
(B) were observed to have increasing mortality rates - same as A, but also increasing mortality rates suggest the numbers keep climbing while the end of sentence terminates at 86 percent. wrong
(C) have been observed to have increased mortality rates - 'have been' here instead of were ties the previous observations to the current disease, answer C
(D) had been observed to have increased mortality rates - had is improperly used. wrong
(E) have been observed to have increasing mortality rates - similar to B with 'increasing'. wrong

brp616 · Answer

IMO C - I chose A in the error log unfortunately, writing the answer I realized it

Went by elimination of answers

A - were observed more implies that the mortality rate applies to the group in a single reading as opposed to looking at the population multiple times, which 'have been observed to have' implies (i.e. the mortality rate is observed frequently and in that time it has been observed to go as high as 86%)

B - mixes past tense (since, were) and present tense (increasing) without a defined time period

C - See answer for why A is wrong, this uses 'have been observed to have' and uses tenses correctly

D - 'had been observed' implies it used to in the past and not now, which is not true

E - See answer for B, increasing is wrong here

12 Days of Christmas GMAT Competition - Day 3: Bitter crab disease is

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