下列程序的执行结果为 Private Sub Command1_C1ick( ) Dim sl As String，s2 AS String s1= abcdef Call lnvert(s1，s2) Print s2 End Sub Private Sub lnvert(ByVal xstr As String，ystr As String) Dim tempstr As Stdng 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