单项选择题

把窗体的KeyPreview属性设置为True,然后编写如下过程:
Private SubForm_KeyDown(KeyCode As Integer,Shift As Integer)
PrintChr (KeyCode)
End Sub
Private Sub Form_KeyUp(KeyCode As Integer, Shift As Integer)
PrintChr(KeyCode+2)
End Sub
程序运行后,如果按“A”键,则输出结果为 ______。

A.A
A
B.A
B
C.A
C
D.A
D