GWD8-41 (number / figure / amount 的修飾?)

[mimieye]

GWD8-41
When drive-ins were at the height of their popularity in the late 1950's, 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

剛剛在看GWD8-41的討論
忽然被 number / figure / amount 該用什麼修飾搞的一團亂
想要請教一下
像是bigger/smaller/less/fewer/more這些字
分別修飾 number / figure / amount的誰呢?
還是要根據前面的名詞單複數決定呢?
根據我的記憶
amount修飾是不可數名詞,所以要用less/more than the amount...,
number 和 figure是指數字的大小,
所以要用bigger/smaller than the number / figure of....
這樣對嗎?
那fewer呢? 是不是也可以修飾amount?
像是GWD8-41好像就是用fewer修飾amount耶
可不可以幫我開示一下, 感恩!