下列各组物质中，化学键类型不同的是（） A．NaCl和HNO3 B．H2O和N_爱下问搜题

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问题多选题

下列各组物质中，化学键类型不同的是（　　）

A．NaCl和HNO₃

B．H₂O和NH₃

C．CaF₂和CsCl

D．CCl₄和Na₂O

答案

A、NaCl为离子化合物且只含有离子键，而HNO₃为共价化合物，含有共价键，化学键类型不同，故A正确；

B、H₂O和NH₃均为共价化合物，化学键类型相同，故B错误；

C、CaF₂和CsCl均为离子化合物，化学键类型相同，故C错误；

D、CCl₄为共价化合物，Na₂O为离子化合物，化学键类型不同，故D正确．

故选AD．

单项选择题

系统实施指的是把系统的（）转换成实际运行的系统的全过程.

A.物理模型

B.逻辑模型

C.程序模型

D.关系数据模型

完形填空

完型填空（共20小题,每小题1． 5分，满分30分）
阅读下面短文，掌握其大意，然后从36—55各题所给的四个选项（A、B、C和D）中，选出最佳选项，并在答题卡上涂黑。
My mother attended college during the day while my sister was in school and I was in daycare．One day at daycare I   36  a tired mother attempt to   37  her daughter．The mother refused her little girl’s request to go to McDonalds for dinner and the daughter immediately 38 over the floor, kicking and screaming, "I want to go to McDonalds．"_39_her mother tried stopped her crying．Finally her mother gave in, the girl stopped crying and they left．To say I was amazed would be   40  ,I was delighted that 41  I wanted could be got in the same way．
That day my mother picked me up early from daycare 42  we were collecting our - Christmas shopping．As we walked through the toy section, I saw a 43 I had to have．It was a white and red telephone whose bells   44  as it was pulled along on a string．
45  lovingly at my mother, I asked, "Mama,   46  I have that telephone?" She replied, "Not now, but if you are a good girl maybe Santa will bring it to you．" As I insisted, her eyes narrowed and her hand 47  on mine．
By now we were standing in the long line, and I figured it was _48_．I lay down on the ground and began screaming．"I want that telephone．" Tired Christmas shoppers looked as my mother   49 said, "Becky, you ’d better get up by the count of three 50 ．"
Nothing happened．So then she lay   51  me on the floor, and began kicking and screaming, "I want a new car, I want a new house, I want some jewelry, I want…" _52_ , I stood up．
"Mama, stop．Mama, get up," I   53  said．
She stood, and   54  herself off．At first astonished, the others waiting in line began to clap．And as they were leaving, they said with a smile, "Your mom got your good．I bet you’ll never try that again．"
And I didn’t, because it left a lasting mental picture more effective than any   55 _ mark．

C．Carrying on

D．Going through

B．accumulated

A．more or less

B．again and again

C．now and then

D．now or never

D．disappointedly

C．or something