单项选择题

在窗体上画一个命令按钮和两个文本框,其名称分别为Command1、Text1和Text2,在属性窗口中把窗体的KeyPreview属性设置为True,然后编写如下程序:   Diln S1 As String,S2 As String   Private Sub Form Load()    Text1.Text=""    Text2.Text=""    Text1.Enabled=False    Text2.Enabled=False   End Sub   Private Sub Form KeyDown(KeyCode As Integer,Shift As Integer)    S2=S2&Chr(KeyCode)   End Sub   Pri vate Sub Form KeyPress(KeyAscii As Integer)    S1=S1&Chr(KeyAscii)   End Sub   Private Sub Command1 Click()    Text1.Text=S1    Text2.Text=S2    S1=""    S2=""   End Sub   程序运行后,先后按“a”、“b”、“c”键,然后单击命令按钮,在文本框Text1和Text2中显示的内容分别为( )。

A.abc和ABC
B.空白
C.ABC和abc
D.出错