Question

  ——　Was that the new comer who walked by?

——　＿＿＿＿＿.

A.It must be that     B.It must have been  C.He must be     D.This must have been

Answer 1

B

解析:

表示对过去情况的猜测，用“情态动词＋have done”；而it代替上文所指的new comer。