What Is the Major Problem Associated with Self-Selection as a Way

Multiple Choice

What is the major problem associated with self-selection as a way to assign participants to the experimental and control groups?

A) The treatment necessarily will work in the experimental group because those participants are especially motivated.
B) The two groups probably will differ on many variables besides whether or not they received the treatment.
C) Self-selection violates the requirement for informed consent.
D) Self-selection prevents the manipulation of the independent variable and measurement of the dependent variable.