下列程序的执行结果为( )。Ptivate Sub Commandl_Click()Dim FirStr As StringFirStr= abcdef Print Pct (FirStr)End SubPrivate Function Pct(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,l) + Mid(xStr,strLen - i+i ,1)i=i + 1LoopPct=tempStrEnd FunCtion
A.abcdef
B.afbecd
C.fedcba
D.defabc