下列程序的执行结果为()。Private Sub Command1_Click() Dim s1 As String s2 As String s1=ab

下列程序的执行结果为()。 Private Sub Command1_Click() Dim s1 As String,s2 As String s1="abcdef" Call Invert(s1,s2) Print s2 End Sub Private Sub Invert(ByVal xstr As String,ystr As String) Dim tempstr As String i=Len(xstr) Do While i＞=1 tempstr=tempstr+Mid(xstr,i,1) i=i-1 Loop ystr=tempstr End Sub

A．fedcba

B．abcdef

C．afbecd

D．defabc

请帮忙给出正确答案和分析，谢谢！