将M克食盐溶液蒸发掉全部水得食盐m克,则M克食盐溶液中溶质的质量分数为（   ）

我国从免除学杂费、免费提供教科书，到免除农村寄宿生住宿费，不断改善农村中小学生学习生活条件，这主要是为了（     ）

How often do you use your car? Can you use your car less often? Do you know the following facts in the UK?
·About 50% of all car journeys are just for fun.
·Over 80% people go to work by car.
·25% car journeys are under two miles.
·70% car journeys are under five miles.
WALKING & CYCLING

Instead of using the car for short journeys, why not walk or ride a bicycle? Walking is the most popular form of exercise—it’s healthy and it can save money. If you work nearby, try walking or cycling instead of driving. Walking your children to school gives them valuable road experience.
BUSES

Bus companies are using new buses: some run on new fuelswhich produce less pollution; some have easier access（通路）for disabled and old people. There are special traffic lanes (行车道)to make bus journeys easier. So do something to help solve the pollution problem----let the bus take you to work and your children to school.
TRAINS

All car journeys, long or short, can be hard work. For some trips, it is wiser to take the train. Leave your car at home and walk, cycle or take a bus to and from the station. Train travel is fast, safe and comfortable. Train tickets are not always expensive.