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…
6)We have good reason to believe that…
There are three reasons for the changes that have takenplace in our life. Firstly,people’s living standard has been greatly improved. Secondly,most people are well paid,and they can afford what they need or like. Last butnot least，more and more people prefer to enjoy modern life.
Great changes have taken place in our life. There are three reasons for this.
1)It has the following advantages.
2)It does us a lot of good.
3)It benefits us quite a lot.
4)It is beneficial to us.
5)It is of great benefit to us.
Books are like friends. They can help us know the world better,and they can open our minds and widen our horizons.Therefore，reading extensively is of great benefit to us. 表示坏处
1)It has more disadvantages than advantages.
2)It does us much harm.
3)It is harmful to us.
However,everything divided into two. Television can alsobe harmful to us. It can do harm to our health and make us
lazy if we spend too much time watching television. 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.
Computers are now being used everywhere,whether in thegovernment，in schools or in business.
Soon,computers will be found in every home,too. Wehave good reason to say that computers are playing an increasingly important role in our life and we have stepped intothe Computer Age.