产力性难产，与下列哪项无关()

A．子宫收缩乏力

B．子宫收缩过强

C．子宫痉挛性狭窄环

D．病理缩复环

E．子宫收缩不协调

下列程序代码段中，在单击命令按钮调用SelMid函数时，其运行结果为( )。
Private Function SelMid(aStr As String)As String
Dim temp As String
Dim sLen As Integer
temp=""
sLen=Len(aStr)
i=1
Do While i＜=sLen/2
temp=temp+Mid(aStr,i,1)+Mid(aStr,sLen-i+1,1)
i=i+1
Loop
SelMid=temp
End Function
Private Sub Command1_Click()
Dim Str As String
Str="abcdef":Print SelMid(Str)
End Sub

A) abcdef B) afbecd C) fedcba D) defabe