Mad cow disease is caused by deformed proteins called prions. Disease is spread when meat from an infected cow is eaten. Prions are composed entirely of protein material and can make natural proteins deform into more prions. After a few years, the brain of an infected person or cow looks like a sponge full of holes. Are prions considered organisms?

a. Yes because they can cause disease.

b. Yes because they make more of themselves.

c. No because they are not made of cells.

d. No because they can't make their own food.