Which of the Following Is TRUE

Multiple Choice

Which of the following is TRUE?

A) External validity is concerned with the issue of whether or not the specific treatment in which the researchers are interested has actually brought about the effect they have observed.
B) A consumer good purchase experiment conducted in a mock-up store is more externally valid than the same experiment in a real store setting.
C) External validity deals with the problem of projecting one's results from the experimental setting to the real world.
D) Both A and C.
E) A, B, and C.