制动系统的作用是什么？
参考答案：（1）使车辆在行使中强制降速，以致停车；
（2）使车辆在下坡时缓行及维持恒速；
（3）使车辆停在原地不致溜车。
[2014·扬州期末]若a1<a2，b1<b2，则a1b1＋a2b2与a1b2＋a2b1的大小关系是________．
根据句子意思，用括号中所给单词的适当形式填空。
1. Our school becomes quiet and _______ (peace) after children leave.
2. Sandy organized a charity show _______ (success) last year.
3. Bill was feeling sad. He told me about his _______ (happy).
4. ______ (sleep) in a blue room is good for your mind and body .
5. Simon just forgot when ______ (meet) his friends
6. Wearing red can help when you are having difficulty ______ (make) a decision.
7. You'd better give up _______ (smoke), it's bad for your health.
8. A year is _______ (divide) into 12 star signs in western countries.
9. Andy is _______ (energy) enough to be a leader.
10. It is silly of you _______ (not forgive) others for their faults.
