double vs twice

[dextar]

CAn any one agin tell me the differnce b/w usage of double and twice ?

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

[amitansu]

I guess, in this context "double" shows to the people and "twice" would show to the number.

I am confused between A and E.

A could be the choice as those refers to young audults !

Please explain if ans is different.

[dextar]

The answer is E . Here we are referring to percentage. So may be twice is appropriate. bTW why is option C out. It is clear and shortest.

[amitansu]

I guess 'twice those' usage is wrong here.Because twice here refers to numer not people.

Moreover, the usage of "those" confuses whether actually referring to people or number.