天山－4－1

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.
A. 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
B. 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
C. 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
D. 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
E. 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
Answer:B

这题实在好混乱，分不请which 从句修饰哪个词，所以最后我选了E，当时是考虑未划线部分的it是单数，所以就在which中选了单数动词，虽然对E中的then also later也持怀疑的。

请问到底which和as it was televised nationwide中的it各指代哪个单词。谢谢先