求助prep语法一题。。。

透明小宇子

When drive-ins were at the height of their popularity in the late 1950s, some 4,000 existed in the United States, but today there are less than one-quarter that many

A. there are less than one-quarter that many

B. there are fewer than one-quarter as many

C. there are fewer than one-quarter of that amount

D. the number is less than one-quarter the amount

E. it is less than one-quarter of that amount

忘了新还是旧prep,我觉得C清晰又简单，但是B为什么是最佳答案？我都没太懂B是个什么构造，是不是含有省略？请各位指点下下………

forevergyx

对啊~这道题为什么啊？我也觉得B好~不是应该是完整结构as many as 吗？