- You talk so much about London. You ________have been there. - Yeah, I went sightseeing on a tour last summer.

—Why are those people gathering in the middle of the street?—I don’t know. There ________ be an accident.

Some young people these days just ________ go out of their homes to contact the real world．

I tried more than once to persuade the taxi driver to slow down, but he just __________ listen.

—What does the sign over there read?—No person        smoke or carry a lighted cigarette, cigar or pipe in this area.