用钼酸铵分光光度法测定水中磷时，抗坏血酸溶液易氧化发黄，如何延长溶液有效使用期？

胸外心脏按压恰当的部位是

A．心前区

B．胸骨下部

C．胸骨中上1/3交界处

D．胸骨中部

E．胸骨角

维护人员应每（）天向除泥器的激震器轴承处加黄油一次。

A、1

B、2

C、3

D、4

Common sense would tell us that physically active children may be more likely to become active and healthy adults.

In the United States, elementary and middle schools are advised to give students two and a half hours of physical activity a week. That is what the Centers for Disease Control and Prevention and the American Heart Association recommend. They say high schools should provide about four hours of physical activity each week.

Yet many schools across the country have reduced their physical education programs. Just this week, a study reported that life expectancy has fallen or is no longer increasing in some parts of the United States. The situation is worst among poor people in the southern states, and especially women. Public health researchers say it is largely the result of increases in fatness, smoking and high blood pressure. They also blame differences in health services around the country.

In 2006, a study found that only four percent of primary schools provided daily physical education all year for all grades. This was true of eight percent of middle schools and two percent of high schools. The study also found that twenty-two percent of all schools did not require students to take any P.E.

Charlene Burgeson , a health expert says one problem for P.E. teachers is that schools are under pressure to put more time into academic subjects. Also, parents may agree that children need exercise in school. Yet many parents today still have bad memories of being chosen last for teams because teachers favored the good athletes in class.

But experts say P.E. classes have changed. They say the goal has moved away from competition and toward personal performance, as a way to build a lifetime of activity. These days, teachers often lead activities like weight training and yoga.

Some parents like the idea of avoiding competitive sports in P.E. class. Yet others surely dislike that idea. In the end, schools may find themselves in a no-win situation.

小题1: The underlined word “expectancy” in Paragraph 3 probably means “       ”                            

A．quality

B．length

C．exception

D．depth小题2:According to the passage which of the following may not lead to poor health?

A．Fatness.

B．Smoking

C．High blood pressure.

D．Health service小题3: What can be inferred after you read this passage?

A．Physical activities are becoming more and more popular in American schools.

B．All the schools provided daily physical education all year for all students.

C．Parents think children need physical education for their bad memories.

D．Students spent less time on physical education for academic pressure.小题4: What is the main idea about this passage?

A．P.E. is the most important subject for all students.

B．P.E has changed its goal for some reasons in America.

C．It introduces us the present situation of P.E in American schools and its cause.

D．P.E can help students improve their academic subjects.

人类总是依据自身的利益评价外部事物，将之分成优劣好坏，而大自然则另有一套行为规范与准则．现在人们闻之色变的沙尘暴，即由于强烈的风将大量沙尘卷起，造成空气混浊，能见度小于千米的风沙天气现象，其实古已有之．它本是雕塑大地外貌的自然力之一，是大自然的一项工程，并且在全球生态平衡中占有一席之地．在地质史上，风力对草原带的风化物质进行筛选分类：凡搬不动的粗大砾石，留在原地形成砾石戈壁滩；颗粒适中的粗砂和细砂被吹移到附近就地聚集成沙漠；颗粒微小的粉沙细土和微尘，则被强上升气流扬上天空，作中长距离的输送．我国黄土高原的黄土层就是沙尘经数百万年堆积而成的，华夏文明就是在这块沙尘累积的黄土地上诞生和发展起来的．澳大利亚的沙尘乘着南半球的西风掠过塔斯曼海，使新西兰火山岛上的土壤更为肥沃，因而被称作“澳大利亚出口的珍贵产品”．从非洲内陆吹向地中海的强风帮助古罗马人使用帆船从埃及运回小麦，但也将撒哈拉大沙漠的沙尘带到意大利、西班牙和法国．沙尘暴固然使空气中的可吸入颗粒物增加，然而由于沙尘含有碱性，又可中和大气中的酸性物质，减缓酸雨的发生．风是地球上空的传送带，它将大陆的沙尘吹向海洋，又将海洋的水汽吹向大陆．沙尘和水汽相遇，便能结合为云，最终化作降水．可见，沙尘不仅在土壤的分布和补充上扮演着重要角色，而且在全球的水循环上也扮演着重要角色．可以说，沙尘也是决定全球生态平衡的因子．然而，近百年来，沙尘暴却已成为影响人类生产生活的一大灾害．构成我国沙尘暴的物质材料，多来自干旱、半干旱的草原区．在人为活动的干预下，特别是由于森林大量砍伐，土地过度开垦，工厂盲目建设，排放不加控制，结果造成生态巨变：原来有沙漠的地方沙漠扩大了；没有沙漠的地方沙漠产生了；内陆河流程缩短，水量减少，沼泽地消失；河流两岸的绿色走廊枯萎死亡．这样，来自大西北的沙尘暴，一路上还源源获得裸地上新的沙尘源的补充，而且混入了工矿企业排放的有害成分和来自草原上牲畜粪便中的病菌病毒．总之，在受到人为因素的干扰后，自然界的风蚀速度已远远大于土壤的生成速度，一连串的灾害也就由此产生．歌德说过：“大自然是不会犯错误的，错误永远是人犯下的．”这或许能给我们某种启示．

下列对沙尘暴的解释，最准确的一项是______．

A．沙尘暴是由于风将大量沙尘卷起，使空气混浊，能见度小于千米的风沙天气现象

B．沙尘暴是雕塑大地外貌的自然力之一，是大自然保持全球生态平衡的一项工程

C．从地质史上看，沙尘暴是风力对草原带的风化物质进行筛选分类的结果

D．沙尘暴是那些颗粒适中的粗砂和细砂被大风吹移到附近就地聚集成沙漠形成的

控制中心报警系统是由（）等组成的火灾报警系统。

A、消防控制室的消防控制设备

B、报警阀组

C、集中报警控制器

D、区域报警控制器

E、火灾探测器