请教GWD31-15-Q1&Q12，多谢！

Q1:

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
4. then also later in the United States House of Representatives, not until 1974 did Barbara Jordan become a nationally recognized figure, as she participated in the hearings on the impeachment of President Richard Nixon, being
5. then also 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 was

答案选的是B, 但是the impeachment是单数，为什么不用was而用were呢？

Q12:

For the farmer who takes care to keep them cool, providing them with high-energy feed, and milking them regularly, Holstein cows are producing an average of 2,275 gallons of milk each per year.

1. providing them with high-energy feed, and milking them regularly, Holstein cows are producing
2. providing them with high-energy feed, and milked regularly, the Holstein cow produces
3. provided with high-energy feed, and milking them regularly, Holstein cows are producing
4. provided with high-energy feed, and milked regularly, the Holstein cow produces
5. provided with high-energy feed, and milked regularly, Holstein cows will produce

答案选的是E, 为什么不选D呢？不明白这里为什么要用将来时态。

Q1 which从句修饰的是hearings，体会一下句意吧，能被televised的应该是hearings

Q12 全句一直用them指代，所以应该用cows

个人观点哈~

谢谢ls,真是厉害，简单清楚~