单项选择题

下列程序的执行结果为
Private Sub Command1_Click()
Dim FirStr As String
  FtrSt="abcdef"
  Print Pat(FirStr)
End Sub
Private Function Pat(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,1)+Mid(xStr,strLen -i+1,1)
    i=i+1
  Loop
  Pat=tempStr
End Function

A.abcdef
B.afbecd
C.fedcba
D.defabc