What Problem Is Shared by the Placebo, Control Method, and the Withdrawal

Multiple Choice

What problem is shared by the placebo, control method, and the withdrawal design method?

A) the concern about withholding treatment from those who need it
B) the issue of tricking people into thinking that they will get better
C) the fact that the individual will likely respond to the unique circumstances of the research setting
D) the lack of control of the independent variable