(A) that the elephant that gave rides to children at the Whipsnade Zoo was earning

(B) that the elephant, giving rides to children at the Whipsnade Zoo, had been earning

(C) that there was an elephant giving rides to children at the Whipsnade Zoo, and it earned

(D) the elephant that gave rides to children at the Whipsnade Zoo and was earning

(E) the elephant giving rides to children at the Whipsnade Zoo and that it earned

Choice A, the best answer, uses the idiomatic construction noted... that and clearly focuses on the salient information-- a comparison of annual earnings. In B, the structure of noted... that the elephant, giving rides ..., had been earning falsely implies that the reader already knows about the elephant--that is, that the existence of this particular elephant is not new information. Also, the past perfect had been improperly places the elephant's earning in the past, prior to Wootton's; consistent verb tense is needed to show that the actions are simultaneous. Choice C may be faulted for distortion of meaning and diminished clarity because it suggests that the point of Wootton's example was the elephant's very existence; comparative earnings are presented (after and) as incidental detail. Choice D is awkward and inexact; the whole circum­stance that Wootton "noted" is best expressed in a clause that begins with that. Choice E does not use the idiomatic construction noted that x; therefore, and that it earned has no parallel construction to which it can be joined.

答案A为什么用过去进行时啊？用一般过去时不就可以了吗？怎么感觉ets出题越来越不严谨了呢？。。。。。。请指教，谢谢！

Yes, I think the past tense should be Ok here.

But in GMAT philosophy, you are required to choose the best answer, not the perfect one. So don't expect ETS to test you with a question in a 严谨 way you prefer.

过去时表示过去某个时点的动作，不具有延续性，跟后面的anually搭配不恰当。而后面的earned是和then以及as。。。搭配的，说明是“作为director那个时候，那个时点”所赚钱的水平，因此用过去时。