能特异地与原核生物RNA聚合酶9亚基结合的抗生素是
A.嘌呤霉素
B.利福霉素
C.卡那霉素
D.氯霉素
E.放线菌酮
参考答案:B
Professor Haley told me that he__________by many of his students at the railway station.
A.had been seen off
B.have been seen off
C.had seen off
D.have seen off
在窗体上绘制一个名称为Commandl的命令按钮,然后编写如下事件过程: Private Sub Commandl Click()c="ABCD"For n=1 To 4 Print ______Next End Sub 程序运行后,单击命令按钮,要求在窗体上显示如下内容: D CD BCD ABCD 则在横线处应填入的内容为
A.Left(c,n)
B.Right(c,n)
C.Mid(c,n,1)
D.Mid(c,n,n)