表示重要、必要、困难、方便、可能
1）It is importantfor sb.to do sth.
2）We think it necessary to do sth.
3）It plays an important role in our life.
例如：
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.
表示坏处
1）It has more disadvantages than advantages.
2）It does us much harm.
3）It i
例如：
However，everything dividesinto two.Television can also be harmful to us.It can do harm to our health and make us lazy if we spend too much time watching televi- sion.
表示好处
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.
例如：
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.