单项选择题

设有如下程序:
Private Sub Form_Click()
Dim i As Integer, x As String, y As String
x="ABCDEFG"
For i=4 To 1 Step-1
y=Mid(x, i, i)+y
Next i
Print y
End Sub
程序运行后,单击窗体,输出结果为( )。

A.ABCCDEDEFG
B.AABBCDEFG
C.ABCDEFG
D.AABBCCDDEEFFGG