【语法问题】在线等，PREP语法的2道问题 Which和 than的用法~~~~~~~~~~~~~~~~~~~~~

mirageseeker

216. (GWD-13-1) Although she had been known as aneffective legislator first in the Texas Senate and later in the UnitedStates House of Representatives, Barbara Jordan did not become a nationallyrecognized figure until 1974, when she participated in the hearings on theimpeachment of President Richard Nixon, which were televised nationwide.有谁能解释一下为什么which这里可以指代hearings？也不是就近啊


Soaring television costs accounted for more thanhalf the spending in the presidential campaign of 1992, a greater proportion than it was in any previous election.
A.    a greater proportion than it was
B.    a greater proportion than
C.    a greater proportion than they have been
D.    which is greater than was so       (B)
E.    which is greater than ithas been

使用than的时候，什么情况下可以省略部分名词？谢谢！