托福机经写作
综合
阅读：critics on releasing SO2 to prevent global warming
1.negative effect on environment, acid rain
2.very expansive
3.limited effect
听力：still a very good solution
1.SO2 only forms acid rain with great amount of vapour at lowest level of atmosphere, no negative effect when releasing so2 at higher level of atmosphere
2.compare to other solusions, inexpansive. example: reducing fuel burning emission, need great scientific break through which is 100 times cost of releasing SO2
3.little temperature reduction have far-reaching positive effect on climate
独立：在rural areas可以比在城市更好的照顾家庭
