粉尘中的水分决定着爆炸的性能，水分越多，爆炸危害性（）。A、越高 B、越低 C、

阅读理解。

     Americans think that travel is good for you . Some even think it can help to solve one of the country’s worst problems—crime .

     Crime worries a lot of people . Every year , the number of crimes goes up and up . They often come

from sad homes , with only one parent at all . There are problems with alcohol(酒精) and drugs(毒品).

     There are many young criminals in prison . But prison doesn’t change them-60 to 70 percent will go

back to crime after they are out of prison .

     One man , Bob Burton , thought of a new idea . In the old days , young men had to live a hard life on

the road . They learnt to be strong and brave , and to help their friends in time of danger . This helped

them to grow into men . So Bob started "Vision Quest ".

     He takes young criminals on a long , long journey with horses and wagons(四轮马车) 3,000 miles

through 7 states . They are on the road for more than one year .

     The young people on "Vision Quest " all have bad problems . Most of them have already spent time in

prison . This is the last chance .

     It’s hard work on the road . The day starts before the sun comes up . The boys and girls have to feed

the horses . Some of them have never loved anyone before . But they can love their horses . That love can help them to a new life .

     Not all young people in “Vision Quest” will leave crime behind them , 30 or 40 percent will be in the

prison again . But that’s a lot better than 60 to 70 percent . Bob is right . Travel can be good for you .

Even today , Americans still say , " Go west , young men . "

1.According to the passage , travel is good for you because it can _______ .

A. change the way of life      

B. help to reduce criminals  

C. make your body strong      

D. get rid of crimes completely

2. Criminals’ characters include_______ .

a. A lot of them are young .  

b. They often don’t have a good family .  

c. They may often drink wine too much and take drugs .

A. a , b        

B. a , c      

C. b , c        

D. a , b , c

3. The young people on “Vision Quest ” have to _______ .

A. get up early and feed the horses      

B. sleep together with their horses  

C. love a comfortable life             

D. work all day and all night

4. The underlined sentence "Go west , young men . " in the last paragraph means _______ .

A. travel can help young men learn how to feed horses  

B. people can learn to be strong and brave on a long journey

C. people can learn how give up smoking on their journey

D. scenes in the west are very beautiful

5. Which of the following is true ?

A. Many young criminals are changed by Bob’s new idea .

B. Young criminals all live a happy life on “Vision Quest”

C. Young criminals are becoming fewer and fewer now

D. All criminals do better after they come out of prison

魏徵说：“求木之长者，必固其根本;欲流之远者，必浚其泉源;思国之安者，必积其德义。”(《谏太宗十思疏》)此句话说明( )

①因果联系是一种先行后续的关系 ②因果联系具有客观性

③原因和结果是有严格区别的 ④原因和结果在一定条件下可以相互转化

A．③④

B．①③

C．①②

D．②④

采用合理的砂率，能使混凝土拌和物( )。

A．获得最大流动性

B．使水泥用量最少

C．保持良好的保水性

D．保持良好的黏聚性

E．获得最大的强度

某综合大楼，建筑高度为48m，地上十层，地下一层，每层建筑面积为1950m²，设有中央空调系统，两部疏散楼梯间，两部电梯，一部自动扶梯。

请分析以上案例，回答下列问题：

(1)该建筑应设几部消防电梯?

(2)该建筑空调系统风管在哪些部位应设置防火阀?

(3)该建筑消防用电设备的配电线路能否采用明敷，如果可以，应满足什么条件?

真皮的主要成分是（）

A.纤维

B.脂肪

C.基质

D.细胞