例： There are three reasons for the changes that have taken place in our
life.Firstly,peoples living standard has been greatly improved.Secondly,most
people are well paid,and they can afford what they need or like.Last but not
least,more and more people prefer to enjoy modern life.
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GRE写作时支持和反对某些观点都需要给出原因，而用来表达原因可以尝试这些比较经典的句式：
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...
例： There are three reasons for the changes that have taken place in our life.Firstly,peoples living standard has been greatly improved.Secondly,most people are well paid,and they can afford what they need or like.Last but not least,more and more people prefer to enjoy modern life.