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Engine noise from boats travelling through killer whales’ habitats ranges in frequency from 100 hertz to 3,000 hertz, an acoustical range that overlaps that in which the whales communicate through screams and squeals. Though killer whales do not seem to behave differently around running boat engines, engine noise from boats can be loud enough to damage their hearing over time. Therefore, _______.
Which one of the following most logically completes the argument?(A) younger killer whales are better able to tolerate engine noise from boats than older whales are
(B) killer whales are less likely to attempt to communicate with one another when boat engines are operating nearby
(C) noise from boat engines may impair killer whales’ ability to communicate
(D) killer whales are most likely to prefer areas where boat traffic is present, but light
(E) killer whales would probably be more successful in finding food if boats did not travel through their habitats
Premises:
Engine noise ranges in frequency that overlaps the range in which whales communicate.
The whales don't behave differently around running boat engines
Engine noise can damage their hearing over time.
Therefore ...
We are looking for a conclusion.
(A) younger killer whales are better able to tolerate engine noise from boats than older whales are
We cannot conclude this. What if young whales have bad hearing and it improves over years as they reach youth but the engine noise impacts hearing in a few months? We don't know enough to say what is their better/best hearing age.
(B) killer whales are less likely to attempt to communicate with one another when boat engines are operating nearby
Not true. The argument says specifically that they don't behave differently when the running engines are around. So we certainly CANNOT conclude that they don't communicate normally when engines are around.
(C) noise from boat engines may impair killer whales’ ability to communicate
The argument tells us that engine noise can damage their hearing over time. This could certainly impair their ability to communicate. Hence this is correct. Noise from engines may impair their ability to communicate.
(D) killer whales are most likely to prefer areas where boat traffic is present, but light
We don't know what they prefer and whether they get disturbed by boat noise. Also, no reason to assume that they prefer areas where boat traffic is present.
(E) killer whales would probably be more successful in finding food if boats did not travel through their habitats
No mention of food finding so irrelevant.
Answer (C)