Which of the following would be the best experimental design? Multiple choice question.

A.)Dr. Smite exposes 10 petri dishes of bacteria to chemical treatment, and 10 dishes in the same room are left untreated. She checks growth on each after 2 days.

B.)Dr. Smite exposes 2 petri dishes of bacteria to chemical treatment, and 2 dishes in the same room are left untreated. She checks growth on 2 dishes after 2 days, and her assistant checks the other two.

C.)Dr. Smite exposes 2 petri dishes of bacteria to chemical treatment. She checks growth on each after 2 days.

D.)Dr. Smite exposes 2 petri dishes of bacteria to chemical treatment, and 2 dishes in the same room are left untreated. She checks growth on each after 2 days.

E.)Dr. Smite exposes 10 petri dishes of bacteria to chemical treatment, and 2 dishes in another room are left untreated. She checks growth on each after 2 days.