4.表示重要、必要、困难、方便、可能
1)It is important(necessary，difficult，convenient， possible)for sb.to do sth.
2)We think it necessary to do sth.
3)It plays an important role in our life.
例： Computers are now being used everywhere，whether in the government，in schools or in business.Soon， computers will be found in every home，too.We have good reason to say that computers are playing an increasingly important role in our life and we have stepped into the Computer Age.
5.表示措施
1)We should take some effective measures.
2)We should try our best to overcome(conquer)the difficulties.
3)We should do our utmost in doing sth.
4)We should solve the problems that we are confronted(faced)with.
例： The housing problem that we are confronted with is becoming more and more serious.Therefore，we must take some effective measures to solve it.
6.表示变化
1)Some changes have taken place in the past five years.
2)A great change will certainly be produced in the world’s communications.
3)The computer has brought about(导致) many changes in education.
例： Some changes have taken place in people’s diet in the past five years.The major reasons for these changes are not far to seek.Nowadays，more and more people are switching from grain to meat for protein，and from fruit and vegetable to milk for vitamins.