1)There are three reasons for this.
2)The reasons for this are as follows.
3)The reason for this is obvious.
4)The reason for this is not far to seek.
5)The reason for this is that...
1)It has the following advantages.
2)It does us a lot of good.
3)It benefits us quite a lot.
4)It is of great benefit to us.
1)It has more disadvantages than advantages.
2)It does us much harm.
3)It is harmful to us.
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.
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.
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 many changes in education.
1)No one can deny the fact that...
2)There is no denying the fact that...
3)This is a phenomenon that many people are interested in.
4)However，that’s not the case.
1)There is a striking contrast between them.
1)It has increased(decreased)from...to...
2)The population in this city has now increased(decreased)to 800，000.
3)The output of July in this factory increased by 15%compared with that of January.
1)People have(take，adopt，assume)different attitudes towards sth.
2)People have different opinions on this problem.
3)People take different views of(on)the question.
4)Some people believe that...Others argue that...