Investigation of the floor of the Black sea (Exampack 1 CR)

bluejay210 wrote:From GMAT PREP EXAM PACK 1

Investigation of the floor of the Black Sea, a saltwater sea connected with the Mediterranean Sea by a narrow channel and remote from other seas, has revealed deposits of freshwater shells dating from 5500 B.C. on an ancient shoreline. That shoreline lies 500 feet below the Black Sea's current level, and the sediment just above it contains the remains only of saltwater creatures. Scientists hypothesize that about 5500 B.C., seawater from the Mediterranean overflowed into the Black Sea basin.

Which of the following would it be most useful to ascertain in order to evaluate the scientists' hypothesis?

A. Whether the body of freshwater whose shoreline was uncovered was less than 500 feet deep
B. Whether the remains of saltwater creatures contained in the layers of sediment that lie just above the ancient shoreline differ significantly from those contained in the topmost of layers of sediment in the floor of the Black Sea
C. Whether any of the freshwater shells show indication of having been used as tools
D. Whether there are traces of an ancient shoreline of the Black Sea that lies significantly less than 500 feet below the sea's current level
E. Whether the remains of the saltwater creatures found in the sediment closely resemble the remains of Mediterranean saltwater creatures from the same period.

[spoiler]OA:E[/spoiler]

Premises:
The floor of the Black Sea has deposits only of FRESHWATER CREATURES, implying that -- at one time -- the Black Sea was composed of fresh water.
The sediment just above the floor contains the remains only of SALTWATER CREATURES, implying that -- at some point -- the Black Sea was transformed from a freshwater body to a saltwater body..

Conclusion: Seawater from the Mediterranean Sea overflowed into the Black Sea basin, transforming the Black Sea from a freshwater body to a saltwater body..

For evaluate CRs, rephrase the answer choices as STATEMENTS.
The rephrase of the correct answer choice will either STRENGTHEN or WEAKEN the conclusion.

Answer choice E, rephrased:
The remains of the saltwater creatures found in the sediment closely resemble the remains of Mediterranean saltwater creatures from the same period.
This rephrase establishes a link between MEDITERRANEAN SEA and the SALTWATER CREATURES whose remains have been found in the Black Sea, STRENGTHENING the conclusion that seawater from the Mediterranean Sea overflowed into the Black Sea basin.

The correct answer is E.

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