[单选题]
The graph shows how the number of
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What is the most likely cause of the change in antibody levels at point X?
A. Primary infection
B. Secondary infection by the same pathogen
C. Infection by a different pathogen
D. Infection by a different pathogen
参考答案:
B
本题详细解析:
Explanation:
A second infection by a pathogen triggers a much faster and more potent immune response, resulting in the production of greater levels of antibodies (Choice B), when compared to primary infection. Primary infection causes a smaller increase in antibody numbers; this is represented by Y (Choice A). Infection by a different pathogen (Choice C) would cause a raise in antibody numbers similar to levels in point Y. Antibiotics do not increase antibody numbers (Choice D).
