– You seem to know much about the city.
– That’s true. I _______ it four times in the last three years.

- You seem familiar with Mr. John?
-Of course, we_______ together for three years in the 1990s.

---I seem to be lost. Could you tell me _____?
---Sure. You can take the No.3 bus to get there.

Robots seem very new to most people. But they have a __51__ history. A Greek scientist made the first robot. You may  52  robots in some movies. The robots in the movies are usually stronger, faster and __53__ than people. In real life, most robots are used in factories. They can do lots of dangerous, difficult or__54__ jobs. Some people can’t look __55_ themselves and robots can help them. For example, some people can’t see, and they use a guide dog to help themselves move. But now scientists are__56__ a robot to help them.
Robots are also used in American hospitals. At one hospital, a robot   57  meals from the kitchen to the sick people’s rooms. It never loses (迷失)its __58__ because it has a map of the hospital in its computer system(系统).__59__ the future, robots will even work in space. But robots will  60  take the place of(代替)people but only work for people. They can, however, help us in a lot of different ways.

— You seem familiar with Mr. John?

 —Of course, we _________ together for three years in the 1990s.

A. have worked     B. were working      C. are working          D. worked