泌尿系结石最有效的预防方法是（）。 A.控制感染 B.调节饮食 C.调节水pH值 D

（8分）近两年来，我国西南、北方、长江中下游等地先后遭遇大范围持续干旱。水是生命之源，我们应该了解水、爱护水资源。

（1）自然界中的水都不是纯水，利用沉淀、      、消毒和蒸馏等方法可以净化水。

（2）有些村庄打深井取用地下水，可用     区分地下水是软水还是硬水，常用      的方法来降低水的硬度。

（3）有些村民往盛有浑浊河水中加明矾和漂白粉，然后作为生活用水，其中明矾的作用是                 ，为了除去河水中的臭味和颜色，可以加入       进行吸附。

（4）小明同学为了探究水的组成，邀请你一起参加水的电解实验，发现两极上都有气泡冒出，其中正极与负极上的气体体积之比约为1：2，经检验，正极上产生的气体是      ，负极上产生的气体是        。得出水是由                  两种元素组成的结论。

按照波特的五力分析模型，下列各项因素中，可能对某家航空公司获取行业竞争优势产生不利影响的有( )。

A．进入航空业需要大量的资本投入

B．航空产业的行业增长率开始处于下降趋势

C．由于廉价航空公司兴起，使得机票价格大幅降低

D．由于许多大型国际企业采用视频会议管理跨国业务，使得商务航空服务需求降低

任务型读写

     Educating girls quite possibly harvests a higher rate of return than any other investment available in

the developing world.Women's education may be an unusual field for economists, but increasing women's

contribution to development is actually as much an economic issue as a social one. And economics, with

its focus on incentives(鼓励), provides an explanation for why so many girls are deprived of(剥夺)an

education.

     Parents in low income countries fail to invest in their daughters because they do not expect them to

make an economic contribution to the family: girls grow up only to marry into somebody else' s family

and bear children. Girls are thus seen as less valuable than boys and are kept at home to do housework

while their brothers are sent to school-the prophecy(预言)becomes self fulfilling, trapping women in a

vicious circle(恶性循环)of neglect. 

     An educated mother, on the other hand,has greater earning abilities outside the home and faces an

entirely different set of choices. She is likely to have fewer but healthier children and can insist on the

development of all her children, ensuring that her daughters are given a fair chance. The education of

her daughters then makes it much more likely that the next generation of girls, as well as of boys, will be

educated and healthy. The vicious circle is thus transformed into a virtuous circle.

     Few will argue that educating women has great social benefits.But it has enormous economic

advantages as well. Most obviously, there is the direct effect of education on the wages of female

workers. Wages rise by 10 to 20 percent for each additional year of schooling. Such big returns are 

impressive by the standard of other available investments, but they are just the beginning. Educating

women also has a significant effect on health practices, including family planning.

可以随表的打开而自动打开的索引是( )。

A．单项索引

B．复合索引

C．结构复合压缩索引

D．非结构化索引

当油箱温度达到（）左右时，必须投用油路水冷器。

A.20℃

B.25℃

C.45℃

D.35℃