根据场景完成对话

A:  A  famous professor from Beijing University will come to our school to give us a speech on how to get along well with parents.

B:  ①  (那太好了!)

A:But I've just heard that he can't come.

B:  ②  (发生了什么事?)

A:An accident happened on his way to our school and he was sent to hospital.

B:  ③  (真是出人意料!)

通信成本核算的目的是（）。

A.加强对员工管理

B.加强成本管理

C.制定通信业务资费

D.核算企业的经营成果