1.A number of factors are accountable for this situation.???

2. A good case in point is ...??

3. As an illustration, we may take ...?

4.Such examples might be given easily.??

5.is often cited as an example.

6. The answer to this problem involves many factors.??

7. The phenomenon mainly stems from the fact that...??

8. The factors that contribute to this situation include...??

9. The change in ...largely results from the fact that...??

10. We may blame ...,but the real causes are...??

11. Part of the explanations for it is that ...??

12.The advantages gained from A are much greater than the advantages we gain from B.

13. Indeed, A carries much weight when compared with B.?

14. There is no doubt that it has its negative effects as well as positive effects.

15.No one can deny the fact that ...??

16. The idea is hardly supported by facts.???

17. Unfortunately, none of the available data shows ...???

18. Once in (a newspaper) , I read of/learnt .... The phenemenon of ... has aroused public concern.

19. I have a friend who ... Should he .... ? Such a dilemma we are often confront with in our daily life.

20. According to statistics proved by ..., it can be seen that .