治疗梅毒和钩端螺旋体病的首选药是（）
A.庆大霉素
B.红霉素
C.四环素
D.青霉素G
E.氯霉素
参考答案：D
I wonder ______, Mr.Smith. We're looking for him everywhere. [ ]
A. where has your son been
B. where your son has been
C. where have you gone
D. where your son has gone
SQL中的DROP，INDEX语句的作用是
A．删除索引
B．建立索引
C．更新索引
D．修改索引
