Here's a problem to solve: How could you scientifically determine the quietest place to study in your school?

Among the 4 following options, which is the correct answer?

- A: Ask your principal where the best place is to study.
 
- B: Survey the student body to see where they like to study.
 
- C: Record the level of decibels in various places in the school, and compare the results.
 
- D: Have everyone be as quiet as possible, and then test the decibels in various places in your school.
 