第9题: [单项选择]Questions 26 to 29 are based on the passage you have just heard.A. Work hard to pay whole attention. B. Use a considerable amount of mental effort. C. Use a moderate amount of mental effort. D. Sit still and give total concentration. 参考答案:C 答案解析:[解析] 26-29 When you listen to a comedian cracking jokes on TV, do you have to work hard to pa
第31题: [单项选择]痢疾杆菌的主要致病因素是()。 A. 侵入的细菌数量 B. 外毒素 C. 神经毒素 D. 侵袭力和内毒素 E. 肠毒素 参考答案:D 答案解析:病原体感染人体并且引起发病的条件有侵袭力(包括黏附因子、定植因子和菌毛)、毒力、病原体数量和变异性。但其中侵袭力是必备条件,它是病原体入侵人体并定居在靶器官,并通过直接侵害组织细胞和释放毒素等引起发病