Available choices: a. cigarettes. b. Malnutrition. c. burning coal. d. Healthy food. e. Exercise. f. Good health. g. Allergies. h. Pesticides.

Fact 1: Immunodeficiency occurs when the immune system is not working properly. Fact 2: Malnutrition , particularly with lack of protein , can cause acquired immunodeficiency. Given the two facts above, what can cause the immune system to not work properly?
Answer:
b.