1)One of the greatest problems facing the 21st century will be what to do with all the rubbish produced in the world.
2) The frequent use of drugs (毒品) is a serious problem among some American young people.
3) To travel abroad is a desire shared by many people, but few can afford to do it.
4) Man still has a lot to learn about the most powerful and complex part of his body-the brain.
5) We had a ling debate as to whether we should spend so much money on space technology.
6) Many people have the bad habit of spending money on impulse.
7) The custom of having one’s marriage arranged by parents has disappeared in many parts of the world but continues in some Asian and African countries.
8) Cheating is now considered to be a major problem in colleges and universities.
9) No agreement was reached as to how the plan should be carried out.
10) True, the cost of living has gone up, but so have the workers ‘wages.
11) I had trouble learning or doing something important to me.
12) She had a little trouble with her typing.
13) Many university students experience severe tension (紧张) as final exams draw near.
14) Until recently this hostile (敌对的) attitude towards daydreaming was the most common one .
15) Many people find it harder and harder to keep up with the radical changes that characterize our time.
16) If this project is to be carried out, we must have all the help that modern technology can supply.
17) When the days seem to go by slowly, you can tell that you’re not enjoying yourself.
18) Large amounts of food imports placed a great strain(负担) on the country’s gold reserve(黄金储备)
19)Corruption(腐败) in government is not tolerated in any country that wants to achieves rapid economic growth and improve the life of its citizens.
20) At first thought, the problem seems far too involved (复杂) , but it can certainly be solved when seriously dealt with .
21) Colleges are not always adjusted to the needs of society to they need reform from time to time.
22) We’re all used to thinking that work provides the material things of life.