The test makers use two different concepts in an attempt to confuse us, but we will not let them. We are given both time of submersion and depth of dive. However, the given relationship between these metrics tells us that they are effectively equal and interchangeable.
To make it less confusing, let's use only depth of dive.
Premise: Dolphins can dive deeper than northern fur seals can. (D > NFS) Premise: Elephant seals can dive deeper than Weddell seals can. (ES > WS)
We need to find the one statement that cannot be true (must be false.) Which of these is in violation of our premises?
A. Could be true. ES > D > WS
B. Could be true. D > WS > NFS
C. Could be true. WS > D > NFS
D. Must be false. D > NFS > ES > W > D. This violates our premise that dolphins can dive deeper than northern fur seals.
E. Could be true. ES > NFS > WS
The passage does not give us a correlation between the two groups. All we have is a hierarchy among each group. The answer choices give us various relationships to test out. The correct answer is the one that contradicts our known hierarchies.