如图所示，AB是⊙O的直径，点C为⊙O外一点，CA，CD是⊙O的切线，A，D为切点，连接BD，AD．若∠ACD=30°，则∠DBA的大小是（　　）

一定条件下，在体积为V L的密闭容器中，一氧化碳和氢气反应生成甲醇：CO（g）+2H₂（g）⇌CH₃OH（g）．如图表示该反应在不同温度下的反应过程．关于该反应，下列说法正确的是（　　）

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.