下列程序的执行结果为 Ptivate Sub Commandl_Click() Dim FirStr As String FirStr= abcdef Print Pct (FirStr) End Sub Private Function Pct(xStr As String)As String Dim tempStr As String,strLen As Integer tempStr= strLen=Len(xStr) i=1 Do While i＜=Len(xStr)-3 tempStr=tempStr + Mid(xStr，i，l) + Mid(xStr，strLen - i+i ，1) i=i + 1 Loop Pct=tempStr End FunCtion
A．abcdef
B．afbecd
C．fedcba
D．defabc