Dr Shortstuff Conducted an Experiment to Raise IQ Scores by Having

Dr. Shortstuff conducted an experiment to raise IQ scores by having experimental subjects eat three bananas each day for a month, while control groups had no bananas. Below are his results (scores = average IQ score for group of subjects) .
Which of the following can you say about the results?

A) The experiment proves that the Dr. Shortstuff's treatment works.
B) The experiment has selection bias problems.
C) All experimental subjects ended up the same whether or not they had the treatment.
D) A and B.
E) B and C.