Two decades after the Emerald River Dam was built, none of : GMAT Critical Reasoning (CR)
Check GMAT Club Decision Tracker for the Latest School Decision Releases http://gmatclub.com/AppTrack

 It is currently 19 Jan 2017, 23:01

### 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

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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# Two decades after the Emerald River Dam was built, none of

Author Message
TAGS:

### Hide Tags

Senior Manager
Joined: 07 Jan 2008
Posts: 412
Followers: 3

Kudos [?]: 217 [0], given: 0

Two decades after the Emerald River Dam was built, none of [#permalink]

### Show Tags

20 Jun 2008, 01:56
00:00

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 2 sessions

### HideShow timer Statistics

Two decades after the Emerald River Dam was built, none of the eight fish species native to the Emerald
River was still reproducing adequately in the river below the dam. Since the dam reduced the annual range of
water temperature in the river below the dam from 50 degrees to 6 degrees, scientists have hypothesized that
sharply rising water temperatures must be involved in signaling the native species to begin the reproductive
cycle.
Which of the following statements, if true, would most strengthen the scientists’ hypothesis?
(A) The native fish species were still able to reproduce only in side streams of the river below the dam where the
annual temperature range remains approximately 50 degrees.
(B) Before the dam was built, the Emerald River annually overflowed its banks, creating backwaters that were
critical breeding areas for the native species of fish.
(C) The lowest recorded temperature of the Emerald River before the dam was built was 34 degrees, whereas
the lowest recorded temperature of the river after the dam was built has been 43 degrees.
(D)Nonnative species of fish, introduced into the Emerald River after the dam was built, have begun competing
with the declining native fish species for food and space.
(E) Five of the fish species native to the Emerald River are not native to any other river in North America.
If you have any questions
New!
Intern
Joined: 10 Apr 2008
Posts: 36
Followers: 0

Kudos [?]: 6 [0], given: 0

Re: CR: UNDER THE DAM [#permalink]

### Show Tags

20 Jun 2008, 02:06
IMO A

OA ??
Director
Joined: 27 May 2008
Posts: 549
Followers: 8

Kudos [?]: 312 [0], given: 0

Re: CR: UNDER THE DAM [#permalink]

### Show Tags

20 Jun 2008, 02:08
IMO A

The native fish species were still able to reproduce only in side streams of the river below the dam where the
annual temperature range remains approximately 50 degrees.

The statement clearly shows that there is a relation between temperature and reproductive cycle of native fish.

All other options fail to establish this relation.
Manager
Joined: 14 Mar 2008
Posts: 127
Schools: Chicago R2
Followers: 1

Kudos [?]: 19 [0], given: 0

Re: CR: UNDER THE DAM [#permalink]

### Show Tags

20 Jun 2008, 02:59
Clear A
VP
Joined: 18 May 2008
Posts: 1286
Followers: 16

Kudos [?]: 411 [0], given: 0

Re: CR: UNDER THE DAM [#permalink]

### Show Tags

20 Jun 2008, 03:25
A must be the OA
lexis wrote:
Two decades after the Emerald River Dam was built, none of the eight fish species native to the Emerald
River was still reproducing adequately in the river below the dam. Since the dam reduced the annual range of
water temperature in the river below the dam from 50 degrees to 6 degrees, scientists have hypothesized that
sharply rising water temperatures must be involved in signaling the native species to begin the reproductive
cycle.
Which of the following statements, if true, would most strengthen the scientists’ hypothesis?
(A) The native fish species were still able to reproduce only in side streams of the river below the dam where the
annual temperature range remains approximately 50 degrees.
(B) Before the dam was built, the Emerald River annually overflowed its banks, creating backwaters that were
critical breeding areas for the native species of fish.
(C) The lowest recorded temperature of the Emerald River before the dam was built was 34 degrees, whereas
the lowest recorded temperature of the river after the dam was built has been 43 degrees.
(D)Nonnative species of fish, introduced into the Emerald River after the dam was built, have begun competing
with the declining native fish species for food and space.
(E) Five of the fish species native to the Emerald River are not native to any other river in North America.
Senior Manager
Joined: 07 Jan 2008
Posts: 412
Followers: 3

Kudos [?]: 217 [0], given: 0

Re: CR: UNDER THE DAM [#permalink]

### Show Tags

20 Jun 2008, 09:30
Many people say only "their choice" without any explanation. GMATClub is place for GMAT test takers discuss, so your contributions are highly appreciated.
Director
Joined: 05 Jan 2008
Posts: 701
Followers: 5

Kudos [?]: 415 [0], given: 0

Re: CR: UNDER THE DAM [#permalink]

### Show Tags

20 Jun 2008, 09:44
Quote:
Since the dam reduced the annual range of
water temperature in the river below the dam from 50 degrees to 6 degrees, scientists have hypothesized that
sharply rising water temperatures must be involved in signaling the native species to begin the reproductive
cycle.

Which of the following statements, if true, would most strengthen ]the scientists’ hypothesis?

Thus we need to look for an option that shows the reduced range as the culprit

(A) The native fish species were still able to reproduce only in side streams of the river below the dam where the annual temperature range remains approximately 50 degrees.-> thus it supports the conclusion
(B) Before the dam was built, the Emerald River annually overflowed its banks, creating backwaters that were critical breeding areas for the native species of fish.-> could be true but this DOES NOT strengthen the conclusion
(C) The lowest recorded temperature of the Emerald River before the dam was built was 34 degrees, whereas the lowest recorded temperature of the river after the dam was built has been 43 degrees. -> we dont know it's affect on the range since maximum temp could be anything
(D)Nonnative species of fish, introduced into the Emerald River after the dam was built, have begun competing
with the declining native fish species for food and space.

(E) Five of the fish species native to the Emerald River are not native to any other river in North America.
_________________

Persistence+Patience+Persistence+Patience=G...O...A...L

Senior Manager
Joined: 26 Mar 2008
Posts: 337
Location: Washington DC
Followers: 2

Kudos [?]: 76 [0], given: 4

Re: CR: UNDER THE DAM [#permalink]

### Show Tags

20 Jun 2008, 09:59
I agree with lexis. My pick is A.
Reason..conclusion..because temp range has been narrowed so native fish are not reproducing. We need some argument to strength our conclusion, clearly only A does strength the conclusion.
Manager
Joined: 09 May 2008
Posts: 102
Followers: 1

Kudos [?]: 19 [0], given: 0

Re: CR: UNDER THE DAM [#permalink]

### Show Tags

20 Jun 2008, 19:15
(A) The native fish species were still able to reproduce only in side streams of the river below the dam where the
annual temperature range remains approximately 50 degrees.
- seems correct
(B) Before the dam was built, the Emerald River annually overflowed its banks, creating backwaters that were
critical breeding areas for the native species of fish.
- irrelevant
(C) The lowest recorded temperature of the Emerald River before the dam was built was 34 degrees, whereas
the lowest recorded temperature of the river after the dam was built has been 43 degrees.
- irrelevant
(D)Nonnative species of fish, introduced into the Emerald River after the dam was built, have begun competing
with the declining native fish species for food and space.
- irrelevant
(E) Five of the fish species native to the Emerald River are not native to any other river in North America.
- irrelevant
Senior Manager
Joined: 07 Jan 2008
Posts: 412
Followers: 3

Kudos [?]: 217 [0], given: 0

Re: CR: UNDER THE DAM [#permalink]

### Show Tags

22 Jun 2008, 21:20
Frankly, I think A weaken then conclusion.
VP
Joined: 17 Jun 2008
Posts: 1397
Followers: 8

Kudos [?]: 290 [0], given: 0

Re: CR: UNDER THE DAM [#permalink]

### Show Tags

23 Jun 2008, 10:30
Since the dam reduced the annual range of
water temperature in the river below the dam from 50 degrees to 6 degrees, scientists have hypothesized that
sharply rising water temperatures must be involved in signaling the native species to begin the reproductive
cycle.

A) The native fish species were still able to reproduce only in side streams of the river below the dam where the
annual temperature range remains approximately 50 degrees.
- > A correctly states that the native species of fish reproduction is subject to temperature hence supports
_________________

cheers
Its Now Or Never

Intern
Joined: 21 Jun 2008
Posts: 23
Followers: 0

Kudos [?]: 10 [0], given: 0

Re: CR: UNDER THE DAM [#permalink]

### Show Tags

23 Jun 2008, 11:27
lexis wrote:
Frankly, I think A weaken then conclusion.

A most strengthens the hypothesis. Lets recap:

Hypothesis: Sharp rises in temperature cause increased reproduction levels
Condition: Range of temperatures used to be "50". Current range is "6". Lets say that:

Pre-dam: temperatures ranged between 10 and 60 degrees (high reproduction)
Post-dam: temperatures now range between, say, 30 and 36 degrees (low reproduction)

The scientists are hypothesizing that the reproduction cycle kicks in once temperatures increase. Naturally, there is a higher chance of a noticeable increase in temperature if annual temps vary between 10 and 60 degrees, than if temps vary between 30 and 36 degrees

Which MOST strengthens the hypothesis?

(A) The native fish species were still able to reproduce only in side streams of the river below the dam where the
annual temperature range remains approximately 50 degrees.

If there is evidence that the fish reproduced in the area with a 50 degree range in temperature, this supports the scientists hypothesis (no reproduction in other areas where the range was much smaller)

(B) Before the dam was built, the Emerald River annually overflowed its banks, creating backwaters that were
critical breeding areas for the native species of fish.

May be true, but has nothing to do with temperature ranges and hence doesn't support the hypothesis.

(C) The lowest recorded temperature of the Emerald River before the dam was built was 34 degrees, whereas
the lowest recorded temperature of the river after the dam was built has been 43 degrees.

Irrelevant because the issue here is not lowest or highest temperature, it is the range of the temperatures. Pre-dam, temperatures could have ranged from 34 to 90, post dam from 43 to 60. It does not address temperature ranges and hence does not support the hypothesis.

(D)Nonnative species of fish, introduced into the Emerald River after the dam was built, have begun competing
with the declining native fish species for food and space.

Could be a cause of a decline in reproduction. BUT it doesnt support the hypothesis

(E) Five of the fish species native to the Emerald River are not native to any other river in North America.

I don't see how this could be relevant in any way!

Hope this helped!
_________________

OBLITERATE THE GMAT!!!

Intern
Joined: 21 Jun 2008
Posts: 23
Followers: 0

Kudos [?]: 10 [0], given: 0

Re: CR: UNDER THE DAM [#permalink]

### Show Tags

23 Jun 2008, 11:33
What is OA btw?
_________________

OBLITERATE THE GMAT!!!

VP
Joined: 03 Apr 2007
Posts: 1367
Followers: 4

Kudos [?]: 612 [0], given: 10

Re: CR: UNDER THE DAM [#permalink]

### Show Tags

23 Jun 2008, 19:06
Premise
-none of the eight fish species native to the Emerald
River was still reproducing adequately in the river below the dam.
-Since the dam reduced the water temperature in the river below the dam from 50 degrees to 6 degrees

Conclusion
- sharply rising water temperatures must be involved in signaling the native species to begin the reproductive
cycle.

Assumption- warmer temp play a role in the reproduction activity of teh fishes

(A) The native fish species were still able to reproduce only in side streams of the river below the dam where the
annual temperature range remains approximately 50 degrees.
>>supports the assumption

(B) Before the dam was built, the Emerald River annually overflowed its banks, creating backwaters that were
critical breeding areas for the native species of fish.
>>> irrelevant

(C) The lowest recorded temperature of the Emerald River before the dam was built was 34 degrees, whereas
the lowest recorded temperature of the river after the dam was built has been 43 degrees.
>>>irrelevant

(D)Nonnative species of fish, introduced into the Emerald River after the dam was built, have begun competing
with the declining native fish species for food and space.
>>> this should affect the population size.Irrelevant.

(E) Five of the fish species native to the Emerald River are not native to any other river in North America
>>irrelevant
Senior Manager
Joined: 07 Jan 2008
Posts: 412
Followers: 3

Kudos [?]: 217 [0], given: 0

Re: CR: UNDER THE DAM [#permalink]

### Show Tags

28 Jun 2008, 11:26
Thanks! OA is A.
Re: CR: UNDER THE DAM   [#permalink] 28 Jun 2008, 11:26
Similar topics Replies Last post
Similar
Topics:
7 About two million years ago, lava dammed up a river in western Asia 6 18 Dec 2015, 01:29
7 To prevent a newly built dam on the Chiff River 6 03 Sep 2015, 02:45
14 Two decades after the Dead Sea Barrier was built, none of 11 20 Feb 2013, 05:23
11 Two decades after the Emerald River Dam was built, none of 11 03 May 2010, 13:15
Building the Glenn Canyon dam on the Colorado river caused 9 02 Aug 2008, 10:03
Display posts from previous: Sort by