题目内容：

it-------- the manager the spoke to you just now/求解
a can be b is C must have been D will be

优质解答

C
从just now可知这个句子是对过去的推测,因此用must have done这一结构.
温馨提醒,the应当是that,这个that也可以换成who.整个句子是“It is ...that/who...”这样一种强调结构.