Mary Jane, a Psychologist, Would Like to Conduct Research in the Form

Mary Jane, a psychologist, would like to conduct research in the form of naturalistic observation of marijuana sales and use among teenagers in her city's poorest neighborhood without their knowledge. What problem does this approach raise?

A) The research may be illegal.
B) People often behave differently when they know they are being observed.
C) The sample is insufficiently representative for naturalistic observation.
D) Study participants tend to want to appear socially appropriate.