Experimentation Is More Useful Than Correlational Research for Testing the Claim

Experimentation is more useful than correlational research for testing the claim that

A) children who view a great deal of television violence are also likely to be unusually aggressive.
B) people who exercise frequently are less likely to suffer from depression than infrequent exercisers.
C) people's friendliness and feelings of happiness are increased by the consumption of alcohol.
D) people who consume excessive amounts of coffee experience higher-than-normal levels of anxiety.