请教

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Q19: GWD-13-1

Although she had been known as an effective legislator first in the Texas Senate and later in the United States House of Representatives, not until Barbara Jordan’s participation in the hearings on the impeachment of President Richard Nixon in 1974 was she made a nationally recognized figure, as it was televised nationwide.

1. later in the United States House of Representatives, not until Barbara Jordan’s participation in the hearings on the impeachment of President Richard Nixon in 1974 was she made a nationally recognized figure, as it was

2. later in the United States House of Representatives, Barbara Jordan did not become a nationally recognized figure until 1974, when she participated in the hearings on the impeachment of President Richard Nixon, which were

3. later in the Untied States House of Representatives, it was not until 1974 that Barbara Jordan became a nationally recognized figure, with her participation in the hearings on the impeachment of President Richard Nixon, which was

莫名为什么选b,我觉得C最好，何况WHICH后怎么是WERE复数？

这里的which跳跃修饰。。

修饰hearings(听证会）

A OF B 结构, WHICH 修饰的是A ,

这一题是the hearings on the impeachment  of  President Richard Nixon , 主要是讲 the hearings ,

至于A 选项, as 好象不是连词吧,IT 不能指代前面的句子?