单击命令按钮时，下列程序代码的执行结果为( )。
Private Function PickMid(xStr As String)As Sting
Dim tempStr As String
Dim strLen As Integer
TempStr=" "
StrLen=Len(xStr)
i=1
Do While i＜=strLen/2
　tempStr=tempStr+Mid(xStr,i,1)+Mid(xStr,strLen-i+1,1)
　i=i+1
Loop
PickMid=tempStr
End Function
Private Sub Command1_Click()
Dim FirstStr As String
FirstStr="abcdef"
Print PickMid(FirstStr)
End Sub

A．abcdef

B．afbecd

C．fedcba

D．defabc