Astudent decides to set up an experiment to see if room temperature affects the rate at which individuals fall asleep. she sets up 10 beds for 10 test subjects. 5 of the beds were placed in a dark room at 69 degrees. the other beds were placed in a bright room at 79 degrees. all of the beds are the same size and have the same type of sheets. she observes and records data for the 10 test subjects for a week. what is wrong with this experiment?

a. the student should have a larger number of beds.
b. there is no way of measuring the outcome.
c. more than one variable is being tested.
d. there is no control set-up.