题干

化学与生活密切相关:  ①市场上销售的咸菜干.酱牛肉.咸水鸭等食品都采用真空包装,目的是为了除去空气,使大多数微生物因缺少____而停止繁殖,同时防止食品发生____(填化学或物理)变化而变质.还可以充入某种保护气来延长食品的保质期,例如薯条等小食品充入____气.

②为纪念人类成功攀登珠穆朗玛峰50周年,中国登山协会业余登山队2003年5月21日再次登顶成功.登山队必备的物品之一是氧气瓶,此时氧气的作用是____,燃料燃烧也需要氧气,这是利用了氧气____的性质.

③用结构示意图表示Cl的核外电子排布____

④矿泉水属于____(填“纯净物”或“混合物”).淡水资源有限,我们需要节约用水,如图中表示节水标志的是____

上一题 下一题 0.0难度 选择题 更新时间:2015-06-02 03:49:03

答案(点此获取答案解析)

氧气,化学,氮气,供给呼吸,支持燃灯,,混合物,B

同类题4

根据短文内容,从短文后面的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

    What should you think about in trying to find your career(职业)? You are probably better at some school subjects than others. ____ A boy who is good at mathematics can use that in an engineering career. ____ So it is important to do well at school. On the other hand, you may not have any specially strong or weak subjects but your records show a general satisfactory standard. ____ Knowledge of history is not required for most jobs but if history is one of your good subjects you will have learned to remember facts and details. This is an ability that can be useful in many jobs.

    ____ If nothing else, you may have learned how to get to work on time, to follow instructions and to get on with older workers. Just as important, you may become interested in a particular industry or career you see from the inside in a part-time job.

    Facing your weak points is also part of knowing yourself. ____ Your school record, for instance, may not be too good, yet it is an important part of your background. You should not be apologetic about it but instead recognize that you will have a chance of a fresh start at work.

A. It is better to face any weaknesses than to pretend they do not exist.

B. A girl who spells well and likes English may be good at office work.

C. He may do well in his future work.

D. Although not all subjects can be used directly in a job, they may have indirect value.

E. Your school must have taught you the skills.

F. These may show strengths (优势) that you can use in your work.

G. If you have had a part-time job on Saturday or in the summer, think what you gained from it.