Because People Who Join Alcoholics Anonymous Control Their Alcohol Problems

Multiple Choice

Because people who join Alcoholics Anonymous control their alcohol problems better than people who do not join,a researcher concludes that Alcoholics Anonymous is highly effective.What is a major limitation on this study?​

A) The research had too many independent variables.
B) ​The research did not have a hypothesis.
C) ​The research did not have demand characteristics.
D) ​People were not randomly assigned to groups.