[单选题]
The graph shows how the number
qa)o 2tanst)9of antibodies changed in an individual's
at9;.s+0eyveh k +)ih+g sfvvblood over tim
+)a;v+h.0 9+vfksv igh tseeye.
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).
