Which option is an example of an observational study?
OA. Having customers who bought a certain type of car answer
questions about their satisfaction
with the car
OB. Asking parents how many times a week their teenagers must be
reminded to do their chores
OC. Testing the effectiveness of a new reading program by allowing a
classroom to
use it and comparing the results with another
classroom that doesn't use it
◇ D. Testing the cholesterol levels of students at a community college