Soaring television costs accounted for more than half the spending in the presidential campaign of 1992, a greater proportion than it was in any previous election.
a greater proportion than it was
a greater proportion than
a greater proportion than they have been
which is greater than was so
which is greater than it has been
答案B正确
我的理解是a greater proportion 是half的同谓语,而it是指costs所占spending的比例,也就是说比例和比例在比较,原句补齐应为half is a greater proportion than it was in any previous election,但是实际是it在原文中无法找到对应的proportion ,所以it was 一定要省略。