An annually conducted, nationwide survey shows a continuing

An annually conducted, nationwide survey shows a
continuing marked decline in the use of illegal drugs by
high school seniors over the last three years.

Which of the following, if true, would provide most
support for concluding from the survey results
described above that the use of illegal drugs by
people below the age of 20 is declining?
(A) Changes in the level of drug use by high school
seniors are seldom matched by changes in the
level of drug use by other people below the
age of 20.
(B) In the past, high school seniors were consis-
tently the population group most likely to use
illegal drugs and most likely to use them
heavily.
(C) The percentage of high school seniors who use
illegal drugs is consistently very similar to the
percentage of all people below the age of 20
who use illegal drugs.
(D) The decline revealed by the surveys is the result
of drug education programs specifically
targeted at those below the age of 20.
(E) The number of those surveyed who admit to
having sold illegal drugs has declined even
faster than has the number who have used
drugs.


Plz explain ur answer.

Thanks
Satya