A national survey conducted annually shows that the use of illicit drugs has continued to decline significantly among seniors in high school over the past 30 years. To conclude from the survey results described above, Human use of illicit drugs is declining,. Which of the following, if correct, will provide the strongest support? ['Changes in the use of illicit drugs by senior students in high school rarely match changes in the use of illicit drugs by others under the age of 20.', 'In the past, seniors in high school have been the most likely to use illicit drugs and the most likely to use them in large quantities.', 'The proportion of senior students in high school who use illegal drugs is very similar to the proportion of all people under 20 who use illegal drugs.', 'The downward trend shown by this survey is the result of a drug education program specifically targeted at people under 20.']