Which of the Following Is a Limitation of the Survey

Which of the following is a limitation of the survey questionnaire studies on drug use among adolescents and young adults?

A) The sample sizes used for research studies are too small.
B) This technique can be used only on students who are in classrooms.
C) The researchers who conduct these studies tend to be biased.
D) The results do not reflect trends in drug use over time due to fluctuating tendencies to overreport or underreport drug use.