----- How about the book you are reading now?
----- Excellent indeed. You can find many problems we have come across _____ in it.

——Will you come to my office when you      your work?  ——Sure.

She was working in the room suddenly she heard a boy crying and ____ out as quickly as she could to see what was happening.

I didn’t hear the telephone ringing. I _____.

When the fans hurried to the airport, they found that the famous singer _____.

Mother blamed the dog for breaking the glass, but in fact I _____.

Explorer Robert Ballard searched the sunken ship---the Titanic for more than 20 years and also, with his cameras, he _____ the hole along the side of the ship which had caused it to fill with water and sink.

Experts suggest that teenagers spend at least 30 minutes exercising, five times a week. Walking and riding your bike _____ , and ______.

“We ______ other possibilities too, such as murder. We ______ until we find convincing evidence.”said Detective Sam Peterson.
A. had looked at; wouldn’t give up      B have looked at; don’t give up
C have considered; haven’t given up     D. have been looking at; won’t give up

— Is there any possible way to help the children get rid of such a bad habit?
— To be honest, it’s very hard, but we ______on this problem.