---Where is your father?

---He isn’t here. He __________ Yushu to help the people in trouble.

A．has gone to

B．has been to

C．went

D．is going

呼吸衰竭的分度的主要指标没有以下哪项（）

A.SaO₂指标

B.PaO₂指标

C.PaCO₂指标

D.发绀程度

E.呼吸频率