GMAT Sentence Correction (SC) | Re: According to surveys by the National Institute on Drug

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


is there a solid reason behind discarding D.??
Is it because they have used as much for countable