问题详情

执行下面的程序，消息框里显示的结果是()。
Private Sub Form_Click()
Dim Str As String,S As String,k As Integer
S=Str
For k=Len(Str) To 1 Step -1
S=S & (Mid(Str,k,1)
Next k
End Sub请帮忙给出正确答案和分析，谢谢！