再生数
参考答案：
是用来描述某种传染病在人群中传播能力的指标，可以分为基本再生数（R0）和实际再生数（R）。
Woman: Listen to me, Joe. The exam is already a thing of the past. Just forget about it. Man: That’s easier said than done. Question: What can we infer from the conversation().
A. The exam was easier than the previous one.
B. Joe is sure that he will do better in the next exam.
C. Joe probably failed in the exam.
D. The oral part of the exam was easier than the written part.
肛门直肠周围脓肿大多来源于（）
