I just like this picture lol

Chris would like to conduct a study on the effectiveness of a new substance-abuse treatment program. he has a sample of participants go through the program and he uses as a comparison group people who did not volunteer for the program but were eligible. chris has used a(n) design for his study.

What would happen to the tides if there was no moon and no sun in the sky?

Why learning about people and places around is important?