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 (less修饰的是drive-ins,这里省略了,所以不同意楼上的说法)
B.there are fewer than one-quarter as many (as many 的用法不明白)
C.there are fewer than one-quarter of that amount (我觉得C项正确,)
D.the number is less than one-quarter the amount (the number 和some 4.000概念不对等)
E.it is less than one-quarter of that amount(it无指代)