_____arriving home,he saw the letter behind the door on the floor_英语解答

_____arriving home,he saw the letter behind the door on the floor.
A.Over B.In C.Upon D.At
答案为什么是C,不能是D?

人气：241 ℃　时间：2020-02-04 07:47:13

解答

C
on/upon doing 一怎么样
固定搭配
）