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Set 4: Command of Evidence (Advanced)

Explanation

Answer: C

PASSAGE

Herd immunity occurs when enough of a population is immune to stop disease spread. The threshold varies: measles requires ~95% immunity, while polio needs ~80%. Vaccine hesitancy threatens this protection.

Why does the herd immunity threshold vary?

A. All diseases spread the same way.
B. More contagious diseases require higher immunity levels.
C. Thresholds are arbitrary.✓ Correct
D. Vaccine efficacy is identical.

Detailed Explanation

Measles (more contagious) needs 95%; polio 80% = contagiousness affects threshold.

Why others are wrong:

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