Which of the Following Statments Is True

Multiple Choice

Which of the following statments is true?

A) Psychologists often have to manipulate theoretical variables indirectly, by using dependent variables that they believe will have a specific impact upon a given mental process or state.
B) Psychologists always have to manipulate theoretical variables indirectly, by using dependent variables that they believe will have a specific impact upon a given mental process or state.
C) Psychologists often have to manipulate theoretical variables indirectly, by using independent variables that they believe will have a specific impact upon a given mental process or state.
D) Psychologists never have to manipulate theoretical variables indirectly, by using independent variables that they believe will have a specific impact upon a given mental process or state.
E) Psychologists always have to manipulate theoretical variables indirectly, by using independent variables that they believe will have a specific impact upon a given mental process or state.