Which of the following is an accurate description of the trend in U.S. adolescents' drug use today?

A. The proportions of eighth-, tenth-, and twelfth-grade U.S. students using illicit drugs declined in the late 1990s and the first years of the twenty-first century.
B. The use of drugs among U.S. secondary-school students began to decrease in the early 1990s.
C. Cocaine is the most widely used illicit drug by U.S. adolescents in the twenty-first century.
D. All of these choices are correct.