对depend on 的主被动造成的wordy很疑惑

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249. The personal income tax did not become permanent in the United States until the First World War;before that time the federal govemment was dependent on tariffs to be their main source of revenue.
A.the federal govemment was dependent on tariffs to be their main source of revenue
B. the federal govemment had depended on tariffs as its main source of revenue
C. tariffs were what the federal govermment was dependent on to be its main source of revenue
D.the main source of revenue for the federal government was dependent on tariffs
E.for their main source of revenue, tariffs were depended on by the federal government
答案：B
解析：
A.EThe phrase was dependent on causes unnecessary wordiness, as does the passive construction in answer choice E.→be dependent on 和be depended on ——wordy
C.这个版本的句子是冗长的，因为它的词序倒置，使得第二句的主语成为介词on的宾语。
D.This version of the sentence nonsensically makes source the subject of theverb was [ dependent on].
E..The passive verb form were depended on is wordy and indirect.

疑惑：
是不是depend on 有特殊的用法或主动表被动之类导致用被动形式wordy呢？
C句不是很能理解冗长的点在哪里转换过来是：哪一种呢？
（1）what the federal govermment was dependent on to be its main source of revenue were tariffs
（2）what the federal govermment was dependent on were tariffs to be its main source of revenue
按解析以及语意理解是（2），但是理解的很困难，希望大佬可以解答，谢谢！！

长丝弓

你的理解有一定道理

猴在学gmat

再顶一下