princess

先给出OG的解释：
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.
也就是说A用的是限定性定语从句，而B用的分词是非限定性的。

princess

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.