---Was it the new school headmaster who walked by ?.A. It must be thatB. It must have

问题补充：

---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：

A. It must be that

(答案→)B. It must have been

C. He must be

D. This must have been

解析：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。