It ____ Jack twenty minutes ____ the mathproblem yesterday

You’ll have an exam soon. I think you should spend ______ time on your homework.

We visited the old woman acold winter morning.

(2013·甘肃兰州名校高三检测)Many people believe that hunger is only a problem in the developing countries.________， it is a problem all over the world.

There have been so many school bus accidents recently._________, people are concerned about the school bus safety much.