段落基本句型构造
1 说明原因段
说明原因段一般出现在图表阐释类和说明现象类作文的第二段，其基本的句型构造是：先用一句话引出下文对现象或问题原因的说明，这是段落的主题句；然后用3～5句话列举2～3点具体的原因，以支持主题句。
例
Directions:For this part，you are allowed 30 minutes to write an essay entitled What Electives to Choose.You should write at least 120 words following the outline given below in Chinese
1.各大学开设了各种各样的选修课。
2.学生因为各种原因选择了不同的选修课。
3.以你自己为例……
第二段：说明原因段
①There are many different factors deciding what electives the students choose.②Among all these factors，the interest of the students plays a very important role.③The students，of courses，would like to learn what he or she is interested in.④Moreover，many students will consider whether they could learn some practical skill by the elective，because nowadays companies are placing emphasis on a candidate’s practical skills.⑤Besides，the ability and the prestige of the teacher is also an important factor influencing the student’s choice.(https://www.daowen.com)
2 说明方法段
说明方法段一般出现在方法对策类作文的第二段（偶尔也会出现在第三段，具体根据提纲），其基本的句型构造是：先用一句话引出下文对解决办法、应对措施或决定因素的说明，这是段落的主题句；然后用3～4句话列举2～3点具体的方法、措施或决定因素，以支持主题句；最后再用一句话对前面的方法做出总结（这句话有时可省略）。
例
Directions:For this part，you are allowed 30 minutes to write a composition on the topic Reduce Waste on Campus.You should write at least 120 words following the outline given below in Chinese
1.目前有些校园内浪费现象严重。
2.浪费的危害。
3.从我做起，杜绝浪费。
第三段：说明方法段
①Considering the seriousness of the problem，it is an urgent thing for us to take effective measures to eliminate waste on campus.②Firstly，we college students must stop wasting water，electricity and food in our daily life.③Secondly，we should learn to be economical and try to avoid spending money on something useless.④Thirdly，we have responsibility to call on all our schoolmates to fight against waste.⑤Only in this way can waste on campus be eliminated in the near future.