First _____ the article once quickly to get the general idea of it; then I will ask you a few questions.[ ]

A. write down      

B. look at        

C. hear of            

D. go through

在窗体上画一个名称为Command1的命令按钮，然后编写如下事件过程：
Private Sub Command1_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)