—I'm going back to see my parents this afternoon.                 

—________.            [ ]

A. It's very nice of her              

B. Help yourself to some fish            

C. Say goodbye to them      

D. Give my best wishes to them        

复用段环组网时，某日光路断，但是倒换不成功，请分析倒换失败的可能原因交叉板板件故障。