第3题: [单项选择]Questions 32 to 35 are based on the passage you have just heard.A. Because many settlements were abandoned. B. Because there were many gold-hungry sailors. C. Because private gold could not be protected by law. D. Because everybody raced for California. 参考答案:C 答案解析:[解析] Why was gold-mining a risky business
第21题: [单项选择]关于立克次体的共同特征,下列说法错误的是 A. 以节肢动物为传播媒介 B. 对多种抗生素敏感 C. 菌体内同时含有DNA和RNA D. 大多仅引起人类致病 E. 以二分裂方式进行繁殖 参考答案:D 答案解析:[解析] 此题考查立克次体的共性。立克次体归为广义上的细菌范畴,大多是人畜共患病原体,以节肢动物为传播媒介或为储存宿主,引起人类发热和出疹性疾病。