下列程序的执行结果为( )。Private Sub Command1_Click()Dim FirStr As StringFirSt= abcdef Print Pat(FirStr)End SubPrivate Function Pat(xStr As String)As StringDim tempStr As String,strLen As IntegertempStr= strLen=Len(xStr)i=1Do While i<=Len(xStr)-3tempStr=tempStr+Mid(xStr,i,1)+Mid(xStr,strLen -i+1,1)i=i+1LoopPat=tempStrEnd Function
A.abcdef
B.afbecd
C.fedcba
D.defabc