The boy was having a class when the earthquake broke out in yushu. He could have been killed if he      with his family.

A．had stayed

B．stayed

C．would stay

D．is to stay

穿第6～1颈椎横突孔，经枕骨大孔入颅的结构是（）

A.副神经

B.椎动脉

C.下腔静脉

D.胸背神经

E.肩胛背神经