一)原因
    1.A number of factors are accountable for this situation.

    A number of factors might contribute to (lead to )(account for ) the phenomenon(problem).

    2. The answer to this problem involves many factors.

    3. The phenomenon mainly stems from the fact that...

    4. The factors that contribute to this situation include...

    5. The change in ...largely results from the fact that...

    6. We may blame ...,but the real causes are... 　

    7. Part of the explanations for it is that ...

    One of the most common factors (causes ) is that ...

    Another contributing factor (cause ) is ...

    Perhaps the primary factor is that …

    But the fundamental cause is that

    二)比较     

    1.The advantage far outweigh the disadvantages.

    2.The advantages of A are much greater than those of B.

    3.A may be preferable to B, but A suffers from the disadvantages that...

    4.It is reasonable to maintain that ...but it would be foolish to claim that...

    5.For all the disadvantages, it has its compensating advantages.     

    6.Like anything else, it has its faults.

    7.A and B has several points in common.

    8.A bears some resemblances to B.

    9.However, the same is not applicable to B.

    10. A and B differ in several ways.

    11. Evidently, it has both negative and positive effects.

    12. People used to think ..., but things are different now.

    13. The same is true of B.

    14. Wondering as A is ,it has its drawbacks.

    15. It is true that A ... , but the chief faults (obvious defects )are ...

    三)批驳

    1)It is true that ..., but one vital point is being left out.     

    2) There is a grain of truth in these statements, but they ignore a more important fact.

    3) Some people say ..., but it does not hold water.

    4) Many of us have been under the illusion that...

    5) A close examination would reveal how ridiculous the statement is. 　

    6) It makes no sense to argue for ...

    7) Too much stress placed on ... may lead to ...

    8) Such a statement mainly rests on the assumption that ...

    9) Contrary to what is widely accepted, I maintain that ...

    四)后果

    1. It may give rise to a host of problems.

    2. The immediate result it produces is ...

    3. It will exercise a profound influence upon...

    4. Its consequence can be so great that...

    五)举例

    1) A good case in point is ...

    2) As an illustration, we may take ...

    3) Such examples might be given easily.

    4) ...is often cited as an example.

    六)证明

    1) No one can deny the fact that ...

    2) The idea is hardly supported by facts.

    3) Unfortunately, none of the available data shows ...

    4) Recent studies indicate that ...

    5) There is sufficient evidence to show that ...

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

    七)开篇

    1) Many nations have been faced with the problem of ...

    2) Recently the problem has been brought into focus.

    3) Recently the phenomenon has become a heated topic.

    4) Recently the issue has aroused great concern among ...

    5) Nowadays there is a growing concern over ...

    6) Never in our history has the idea that ... been so popular.

    7) Faced with ..., quite a few people argue that ...

    8) According to a recent survey, ...

    9) With the rapid development of ..., ...

    八)结尾

    1) From what has been discussed above, we can draw the conclusion that ...

    2) It is high time that strict measures were taken to stop ...

    3) It is necessary that steps should be taken to ...

    4) In conclusion, it is imperative that ...

    5) There is no easy method, but ...might be of some help.

    6) To solve the above-mentioned problem, we must ...

    7) In summary, if we continue to ignore the above-mentioned issue, more problems will crop up.

    8) With the efforts of all parts concerned, the problem will be solved thoroughly.

    9) We might do more than identify the cause ; it is important to take actions to ...

    10) Taking all these into account, we ...

    11) Whether it is good or not /positive or negative, one thing is certain/clear...