How do you spend your time at school? Do you know how students in other countries study every day? Here are the studying ways in some western schools.

American Students

    American students spend seven hours in their schools every day. And the day is divided（划分） into classes of about 40 to 50 minutes. Students study English, history, math, science, art and foreign languages. They go to listen to different lessons taught by different teachers in different classrooms. After class they learn job skills. Sometimes they study by working in an office, a hospital or other places one day a week.

German Students

    German students love practicing. Lots of schools have lessons for only half a day. They spend most time practicing. Teachers give students enough freedom. Students may try all kinds of ideas they have. They begin to plan what they will do in the future and work hard at a young age.

French Students

    French students like independence（独立） and freedom. Their school life is very relaxing and interesting. When they have tests, they may have snacks. For example, they can put a few desks together, and put some peanuts （花生）or candies on them.

如图是科学工作者对我国北方地区森林、草地和荒漠地面积变化的调查结果．这对分析说明我国今春以来华北要区多次出现的沙尘暴天气有很大帮助．

（1）请根据调查结果，分析植被和沙尘暴形成的关系．____ 

（2）请根据生态平衡原理提出治理沙尘暴的措施．____．

下图反映了亚洲某国人口增长与构成的变化及其发展趋势。回答下列各题。