51. 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
(B) to double the number the 1977 survey reported
(C) twice those the 1977 survey reported
(D) twice as much as those reported in the 1977 survey
(E) twice the number reported in the 1977 survey

I assumed that E would be incorrect because the statistic tells us about a specific percentage of some number of adults, leading me to choose "twice as much" (a non-count word). With statistics like this, do you always use "countable" words? Answer: E

Thanks for your help.