I had a hard time understanding why (A) is the right answer. After thinking about it for a day on and off, I came up with this reasoning. Please take a look if my logic behind getting the right answer is correct.

I wonder if this this question can be viewed as Resolve Reconcile type; the premise says the land-dwelling whales needed hind limbs capable of supporting its weight, and conclusion says the fragile limbs of whale found in the fossil is the remnant of whale once lived on land. But I tried to solve it as strengthen question.

This question talks about whales from three different periods; ancient whale (lived before fossilized whale skeleton), fossilized whale, and modern whale.

Premise:

Conclusion: The fragile hind limbs are remnants of limbs that land-dwelling whale once had.

I initially misunderstood the conclusion as the fragile hind limbs found in the fossil is the remains the whale that was living on land. So land-dwelling whale having fragile limbs is contradiction within the premise... but the correct understanding is the fragile hind limbs newly found in fossil is how the ancient whale evolved to be. The key was a correct understanding of the word "remnant."

So, to summarize it... whale evolution is like this chronologically.

Ancient Whale (ones lived before the newly found fossilized skeleton)

Fossilized Whale

Modern Whale

So, we need to strengthen the conclusion that the fossilized whale skeleton that has fragile limbs is the evolved form of whales limbs that lived on land at one point.

(A) is correct. The confirmation that ancient whale had a full pelvis would strengthen that by evolution it became a partial pelvis (as found in fossil) and now only bare remnant of pelvis.

(B) This weakens the conclusion

(C) irrelevant

(D) I initially chose this answer and that was because I misunderstood what the conclusion meant precisely.

(E) irrelevant.

It became a quite long explanation... I wonder if I am overthinking when it is really a simple question. I would appreciate any confirmation or correction on my reasoning. Thanks!!