Mr. Smith gradually _____ a knowledge ofthe subject.

Mr Zhu, can I go to meet you at four tomorrow afternoon?–All right, I _____ to my office from a conference by then．I will be waiting for you there

Susan thought ____not easy to answer all thesequestions.

Who _______ the toy train to you —-My uncle ______.

The reason ________ he was late for the meeting is ________ his car broke down on the road.