问题 选择题

三聚氰胺的结构如右图.“三聚氰胺”,有个貌似美妙的别名“蛋白精”,某些广告中曾公然标榜“能提高产品蛋白含量”.三聚氰胺性状为纯白色单斜棱晶体,无味,密度1.573g/cm3.(16℃)常压熔点354℃(分解);快速加热升华,升华温度300℃,溶于热水,微溶于冷水.关于三聚氰胺,下列说法不正确的是(  )

A.是蛋白质

B.是有机物,有弱碱性

C.将购回的奶粉溶于热水后冷却,过滤,可以粗略检测其中是否含有三聚氰胺

D.可以与盐酸反应

答案

A.该物质只含C、H、N三种元素,相对分子质量较小,而蛋白质还含O元素且属于高分子化合物,所以该物质不是蛋白质,故A错误;

B.该物质含C元素及氨基,则是有机物,有弱碱性,故B正确;

C.溶于热水,微溶于冷水,降温析出固体,则购回的奶粉溶于热水后冷却,过滤,可以粗略检测其中是否含有三聚氰胺,故C正确;

D.含氨基,能与盐酸反应生成盐,故D正确;

故选A.

完形填空

Have you ever regretted doing something you shouldn't have done or something you didn't do which you should have? At one time or another we probably all have.There's no __51in getting depressed about it now—it's no __52 crying overspilt(溢出的)milk.However,there may be some gain in thinking about exactly what happened and why __53  we might be able to draw some conclusions for the future.

One thing we all do now and again is to lose our __54 with a friend or close relative.The odd thing is that we more often display great __55 towards someone we are fond of than towards __56 .The explanation may be that we see friends and relatives as a kind of safety net, an opportunity to __57 a bit of steam in a safe environment,while the consequences (后果)of __58   a stranger could be far more serious.

Being honest is usually thought of as a virtue (美德) and undoubtedly this is the __59  .On the other hand,we have all experienced occasions when we have spoken our minds to someone,telling them exactly what we feel,and then have found ourselves filled with feelings of __60 .Perhaps we should have kept our mouths shut?

51. A. reason        B. purpose      C. point          D. result 

52. A. use           B. help         C. value          D. benefit 

53. A. so            B. because      C. but            D. though 

54. A. mind          B. memory       C. manner         D. temper 

55. A. anger         B. interest     C. love           D. respect 

56. A. strangers     B. friends      C. relatives      D. colleagues

57. A. run through   B. throw away   C. give up        D. let off

58. A. inviting      B. insulting    C. speaking to    D. believing in 

59. A. issue         B. case         C. event          D. factor 

60. A. excitement    B. happiness    C. pride          D. guilt 

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