Explanation

Reading the question: This prompt starts off in a friendly manner but starts to get complicated near the end of the prompt. We can parse the prompt at the word "surprisingly." The surprise has two portions: before and after that word. The latter part is shorter, so we can start there. 2) Elephants visit the graves of stranger elephants. Why is that surprising? Because of everything before "surprisingly." Namely, because there is a theory that 1) they observe burials only of animals with which they've had a direct relationship--i.e., not stranger elephants. Point 1) involves burial of friends, while point 2) involves burial of strangers. A good explanation will connect to both points without contradicting them.

Applying the filter: Choice (A) touches on both 1) and 2), in that it may imply that strangers could be friends. However, Choice (A) introduces the idea of empathy without connecting it to burial. It's missing a critical phrase like, "and empathy is what motivates elephants to observe burial rituals." Another problem with (A) is that it doesn't explain why elephants bury some non-elephants, but not others. So (A) is out. Choices (B), (C), and (D) fail to touch on both points 1) and 2). Choice (B) essentially restates the mystery without adding any information. Choice (C) discusses animals that elephants do not bury, so it's not comparing points 1) and 2), which both involve burial. Choice (D) may be tempting, but it doesn't address the fact that elephants visited the graves elephants "they never knew in life," since (D) discusses elephants who were "previously members of a herd and known to that herd." It doesn't hit on any point of 2), stranger burials. Choice (E) connects to 1) and 2) and resolves the friend or stranger burial question. Namely, the true determinant of burial isn't friend or stranger; it's the ability to empathize, which can extend to known humans or unknown elephants. Comparing (E) with (A), we can see that it is much more explanatory. Unlike (A), (E) specifically connects empathy to the act of burial, and it also explains why elephants can empathize with some non-elephants but not others. The correct answer is (E).