What did Zhai Zhigang do while he was doing “walking” ____? — He ____ our national flag to the world

It is well known that Thomas Edison _______ the electric lamp.

Oh, there are so many bottles. All of them are full _____ water.—- Yes，but who filled them ______ water

You seem to be familiar with New York —I _______ there for three years It’sgreat to be back

We all know for sure ____ different life today is from that of the past [ ]