Questions Refer to the Following Research Study

Multiple Choice

Questions refer to the following research study:
Ronda would like to assess the effects of a reading comprehension course on the scores of students. She gives a group of remedial students a reading comprehension pretest and then randomly assigns them to either the treatment group or the control group. Shortly after the treatment, she measures their reading comprehension scores again.
-Suppose Ronda finds out that participants in the treatment group were helping participants in the control group with their reading comprehension. Ronda should be worried about which threat to internal validity?

A) Selection
B) Experimental mortality
C) Testing
D) Diffusion of treatment