第18题: [单项选择]梅毒的潜伏期一般为() A. 24小时 B. 1~2天 C. 3~7天 D. 2~4周 E. 3~7个月 参考答案:D 答案解析:梅毒是由苍白密螺旋体引起的全身性性传播疾病,潜伏期约2~4周。
第19题: [单项选择]{{I}}Questions 11 - 13 are based on the following conversation. You now have 15 seconds to read Questions 11 - 13.{{/I}}What service must be paid for A. Computer classes. B. Training sessions. C. Laser printing. D. Package borrowing. 参考答案:C