C
This question seems more difficult than it actually is, mostly because of the use of several proper nouns.
The argument states that because two whale species (their names and the locations are not important) are now crossing paths during their migration, scientists can gather data that they were previously unable to obtain. The question asks for an explanation for this, so the correct answer must offer some reason why the scientists are able to gather new data.
A is incorrect because it does not offer any reason why the scientists may now gather new data. Also, A fails to take into consideration that it would still be possible to gather data even before migration records were kept.
B, like A, does not offer a reason why the scientists may now gather new data. If the paths of the whales were not consistant over time, the whales could have met before.
C is correct because it offers a reason why the scientists may now gather new data. If both whales never meet, they will not use a frequency to communicate with each other. Since the whales are now crossing paths, they emit a new noise, which scientists can record.
D offers no explanation and has nothing to do with the argument.
E is incorrect. Not only does D not provide any explanation as to why the scientists may now gather new data, it also casts doubt on whether or not scientists could previously gather any data.
I hope that helps