Kwashiorkor is caused by __________.

The correct option is D

imbalance in diet

The correct option is (D):

Explanation of correct option:

1. Kwashiorkor is a disease that results from PEM.
2. Protein-energy malnutrition (PEM) is a term used to describe die that lack protein and energy-giving carbohydrates in the diet.
3. Symptoms of Kwashiorkor are: Protruding belly, dark and scaly skin, brownish hair, stunted growth, swollen legs due to accumulation of water, anemia, and mental retardation.

Explanation for incorrect options:

Option (A):

Smoking causes lung disease.

Option (B) :

Worms are animals that live as a parasite (organisms that depend on another organism for food and shelter) in the intestine of the host (person in which the parasite live).

Option (C):

Viruses are the organisms that cause various diseases such as rabies, and AIDS.

Final answer: Kwashiorkor is caused by an imbalance in the diet.