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问题 选择题

不漏气的橡皮氢气球由地面上升过程中，球内气体的质量与密度的变化情况是：

A．质量增加，密度增加

B．质量不变，密度减小

C．质量减小，密度减小

D．质量不变，密度不变

答案

答案：B

题目分析：由于气球是密闭的，所以内部气体的质量不变，但升空过程中，外界大气压减小，所以气球的体积会增大，从而气体的密度减小，所以B符合题意。

单项选择题

145 –14726岁初孕妇,现妊娠40周,近半月头痛,眼花,今晨出现剧烈头痛,并呕吐两次,来院就诊

A．既往无头痛史

B．既往血压正常

C．有高血压家族史

D．有患病毒性肝炎史

E．有多次泌尿系统感染史
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单项选择题

In the following essay, each blank has four choices. Choose the most suitable one from the four choices and write down in the answer sheet.

The key to SNMP (71) is its simplicity. It has a small command set that does a good job of collecting information from (72) any network device. In a SNMP environment, (73) of the work is handled by the network management system. Devices that are being managed are not (74) with processing (75) that might affect their performance.

72（）

A．many

B．almost

C．a lot of

D．nearly
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