SAT Subject Biology Practice Question 61: Answer and Explanation

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Question: 61

5. Which of these would a researcher test the blood for to determine if a person has been infected with a virus in the past?

A. Antigens
B. Antibodies
C. Macrophages
D. Pathogens
E. Natural killer cells

Correct Answer: B

Explanation:

Antigens or immunoglobulins produced by B and T cells are specific and provide a "memory" that helps to fight previously encountered pathogens, or infectious organisms. Antigens, produced by pathogens, would not linger in the blood. Macrophages and natural killer cells are part of the innate immune system and would not be specific to a particular virus.

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