问题 选择题

推理是一种重要的学习方法.下列推理中正确的是(  )

A.MnO2是加快H2O2分解的催化剂,因此催化剂是加快化学反应速率的物质

B.单质是由一种元素组成的,因此由一种元素组成的纯净物一定是单质

C.氧化物中含有氧元素,因此含有氧元素的纯净物一定是氧化物

D.分子是构成物质的微粒,因此物质都是由分子构成的

答案

A、MnO2是加快H2O2分解的催化剂,但并不是所有的催化剂都是加快化学反应速率的物质,故A错误;

B、单质是指由一种元素组成的纯净物,所以单质是由一种元素组成的,因此由一种元素组成的纯净物一定是单质,故B正确;

C、含有氧元素的纯净物不一定是氧化物,例如氯酸钾中含有氧元素就不是氧化物,故C错误;

D、分子是构成物质的微粒,但是物质不都是由分子构成,还有原子和离子,故D错误.

故选:B.

判断题
完形填空

It is well that young men should begin at the beginning and occupy the least important positions.21  of the leading businessmen of Pittsburgh had a serious responsibility placed upon them at the very  22  of their career.They were  23  to the broom(扫帚), spending the first hours of their business lives   24 the office.

And here is the basic  25  of success, the great secret:  26  your energy, thought, and capital (资本) wholly on the business in which you are  27 .Having begun in one line, determine to fight it out on that  28 , to lead in it, adopt every  29  , have the best machinery, and know the most about it.

The companies which fail are those which have 30  their capital, which means that they have scattered their brains  31  .They have investments in this, or that, or  32  , here, there, and everywhere.“Don't put all your eggs in one basket” is all  33 , I tell you.“Put all your eggs in one basket, and then  34  that basket”.Look round you and take  35 ; men who do that do not often fail.It is easy to watch and carry the one basket.It is trying to carry too many baskets  36 breaks most eggs in this country.He who  37  three baskets must put one on his  38  , which is likely to fall down.One  39  of the American businessman is lack of concentration.

Remember: put all your eggs in one basket, and watch that basket. 40  Emerson says, "no one can cheat you out of final success but yourselves."

21.A.None         B.Few              C.All          D.Many

22.A.beginning      B.end           C.point           D.promotion

23.A.ordered        B.promoted           C.introduced            D.stated

24.A.sweeping out   B.taking out      C.bringing out       D.picking out

25.A.inspiration     B.condition            C.plan              D.case

26.A.concentrate    B.devote             C.apply        D.bury

27.A.charged        B.engaged            C.prepared     D.done

28.A.position      B.career           C.row          D.line

29.A.improvement   B.chance           C.learning      D.rise

30.A.gathered     B.forbidden          C.got          D.scattered

31.A.also          B.either            C.neither        D.yet

32.A.one            B.the other          C.others       D.the others

33.A.apparent      B.clear            C.wrong       D.perfect

34.A.notice       B.observe            C.stare         D.watch

35.A.notice        B.comment         C.interest       D.concentration

36.A.what          B.that               C.whoever      D.whichever

37.A.brings         B.takes              C.carries       D.owns

38.A.mind         B.brain              C.head         D.hand

39.A.fault          B.advantage          C.pattern       D.model

40.A.When         B.While              C.Which       D.As