The OA reasoning is :-
At first, this sentence may sound perfectly fine. But there is a minor issue here with the logic of this sentence. The naked mole rate is not unique "because" of its ability to run backwards; the fact that it can run backwards is the way in which it is unique, not the cause of its uniqueness. "Because" can only be used in actual causal relationships. For example, "He was wet because he got caught in the rain," or "She was warm because she was wearing a coat." When talking about a certain trait, it makes more sense to use "in that." For example, "This painting is special in that it is the only portrait drawn by this artist."
The other problem with this sentence is that it uses the word "which" incorrectly. The word "which" must be proceeded by a comma and refer to the noun phrase immediately before the comma, or else it is wrong. Here, the word "which" must refer to the ability of the rat, but the phrase before the word "which" doesn't specifically refer to the ability. We'll need an answer choice that fixes this problem.
Scan and Group the Answer Choices:
There is a clear and useful 2-2-1 split here, based on the first few words of each choice. (A) and (B) both begin "because," (C) and (D) both begin "since," and choice (E) begins "in its ability."
Eliminate Wrong Answer Choices:
Based on the information we gathered in steps one and two, our path is clear. We can rule out (A) and (B) because they both use the word "because." Similarly, we can rule out choices (C) and (D), because "since" also cannot be used unless the sentence describes an actual causal relationship. This leaves us with Answer Choice (E), which must be correct. When we read it back into the original sentence, we see it solves all the problems we originally spotted, including the problem with the word which. It simply replaces the word "which" with the phrase "this skill," a substitution which clarifies the situation.
There are other problems with the other answer choices. Both choices (A) and (B) use the word "which" incorrectly. Choices (C) and (D) both change the meaning of the sentence; saying the rat runs "equally efficiently" or "as well" backwards and forwards is not identical in meaning to saying that the rat runs "as fast" backwards and forwards
However, I am bit confused between C and E. I get E is better because of meaning issue. I am somewhat not clear why since is wrong.