According to the Study by Lloyd Johnston and His Colleagues

Multiple Choice

According to the study by Lloyd Johnston and his colleagues at the Institute of Social Research at the University of Michigan monitoring the drug use of America's high school seniors in a wide range of public and private high schools, the percentage of illicit drug use:

A) has declined since the late 1990s.
B) has increased since the late 1990s.
C) has been at the same level since the late 1990s.
D) has declined since the late 1990s but started to increase again in the last two years.