There is certain relationship between two given words on one side of : : and…

Concept: In this analogy, the second word in each pair names the entity that is affected by — or undergoes — the condition named by the first word, not the agent that causes it and not the general category the condition belongs to. To complete the pair, find the entity on which the same kind of effect occurs.

Application: Contamination is the harmful condition that occurs in food — food is the entity that gets contaminated. Applying the same relation, infection is the harmful condition that occurs in the body — the body is the entity that gets infected. So the missing word must name the entity affected by infection.

Contrast: Each remaining alternative fails the same affected-entity test:

• Diseases names the broad category of harmful outcomes, not the specific entity undergoing the harm — the pair needs an affected entity, like food, not a category of harm.

• Germs names the agent that causes infection, not the entity that suffers it — this repeats the causal-agent role, not the affected-entity role that food fills in the pair.

• Microbes, like germs, is a causal agent of infection rather than the entity affected by it, so it fails the same affected-entity role test.