Despite the Limitations of Survey Questionnaires, When Can They Be

Despite the limitations of survey questionnaires, when can they be informative?

A) If they are done year after year, because we can then look for changes over time.
B) If they seek information regarding those who are not included in the survey.
C) If they ask questions regarding alcohol use, because it is not illegal.
D) If they ask about the misuse of prescription drugs.