说明原因的句型：

1. There are     two     good reasons    for.....

                         some                               to......

                         many

Example: There are two reasons for the changes in people’s living conditions. First, we have been carrying out an opening and reform policy. Second, our national economy is developing rapidly and the birth rate has been put under control.

2. We have two good reasons for…
Example: We have many good reasons to object to smoking in public places.

3. The reason for…is that +
Example: The reason for my being late was that I missed the bus.

4. Several factors are responsible for the phenomenon.
5. Their opinion is based on the fact that…
6. Those who are in favor of the …believe that…
7. These/ The following are my reasons for my choice.