题目

如图所示，在光滑水平面上有A、B两球，中间连一弹簧，A球固定，今用手拿住B球将弹簧压缩一定距离，然后释放B球，在B球向右运动到最大距离的过程中，B球的加速度将                 ，B球的速度将                ，弹簧的弹性势能将                ． 答案：先变小后变大；先变大后变小；先变小后变大   根据短文内容，按要求完成下列各题。It is a big job to take away a city’s rubbish. Every day trucks come into a city to collect it. Most rubbish is made up of things we can’t eat or use. If we kept these things, we would soon have a mountain of rubbish. In most cities, the rubbish is collected and taken outside of cities to a dump. Often the city dump is placed where the ground is low or there is a big hole. The kitchen rubbish is broken into small pieces and sent into the sewage system (污水系统). The sewage system takes away the used water from toilets, bathtubs and other places.To keep mice and flies away, some earth is used to cover the newly dumped rubbish. Later, grass may be planted on the rubbishfilled land. Finally, a house or a school may be built there, and then you’d never know that this was once an old rubbish dump.In other cities the rubbish is burnt in special places. The fire burns everything but the metal. Sometimes the metal can be used again in factories where things are made of metal. The food parts of rubbish are put in special piles where they slowly change into something called humus (腐殖质), which looks like black earth. It is rich with the kinds of things that feed plants and help make them grow.1题完成句子；2～3题简略回答问题；4题找出并写下全文的主题句；5题将文中划线句子译成汉语。【1】People often put the city dumb in a place where the ground is low or there is _________.【2】Why do people use some earth to cover the newly dumped rubbish? ______________________________________________________________________【3】What can the food parts of rubbish change into?______________________________________________________________________【4】______________________________________________________________【5】_____________________________________________________________