---Was it the new school headmaster who walked by ?

--- _____.

A．It must be that

B．It must have been

C．He must be

D．This must have been

脑疝形成的机理关键在于

A．颅内内容物体积增加
B．颅内血容量增加
C．颅内脑脊液量增加
D．腰椎穿刺放出脑脊液
E．颅腔内压力分布不均