疑问关于“比较结构常出现的数字比较” 求解答！！！！！！！

Rain's

2.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  
答案B   （已经知道4000是代词指代4000 drive-ins


4000 drive-ins是可数，所以that amount错误；that many错误，正确的是用as many，它可以当一个数目来用，这里指代4000 drive-ins。
One quarter as many，是可数，因为分数短语的单复数要看核心名词的单复数，所以这里只能用fewer

Rain's

According to surveys by the National Institute on Drug Abuse, about 20 percent of young adults used cocaine in 1979, doubling those reported in the 1977 survey.
(A) doubling those reported in the 1977 survey
Doubling引导伴随或结果状语，修饰前面整个分句。double应该是指百分比这个数值,而不是young adults,句子相比较的也是百分比的变化,所以those不对,应该是doubling the number reported in the...比较精确
(B) to double the number the 1977 survey reported
To double表目的？意思肯定不对
(C) twice those the 1977 survey reported   
应该是twice as many as those才对
(D) twice as much as those reported in the 1977 survey   
as much as与后面的those矛盾；
(E) twice the number reported in the 1977 survey      
     If the noun in question is already an explicitly numerical quantity, then you should use neither "much" nor "many". Instead, you should just use "twice" or "double" by itself.
其中twice跳跃used cocaine修饰20 percent of young adults.

Dylan7788

顶！同问啊！楼上的同学这个回答不能解决问题。。谁能有更加系统化的总结什么的吗