问题
选择题
---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
答案
答案：B
考查问题回答，问句是it为主语，回答也是it为主语，而且是对过去情况的推测，选B，句意是：--刚刚走过的是校长吗？--一定是。It must have been ="It" must have been the new school headmaster。