根据CT工作原理，X线穿过人体后首先被接收的部件是（） A.计算

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问题单项选择题 A1/A2型题

根据CT工作原理，X线穿过人体后首先被接收的部件是（）

A.计算机

B.照相机

C.磁盘

D.探测器

E.阵列处理机

答案

参考答案：D

解析：在控制台操作下，检查床将人体送入扫描架内，X线球管和探测器围绕待检层面同步旋转，探测经过人体后残存的X线强度，通过模／数转换，以数字信号形式传递给计算机，计算机再通过数／模转换．以电信号形式在显示屏上再现扫描层面图像。

阅读理解

In every country, there are thousands of people who want to help out. Many join organizations run (管理) by their governments, for example, the Peace Corps in the United States and Voluntary Service Overseas in Britain. Since the powerful (猛烈的) earthquake took place in Sichuan, more than 200 thousand volunteers across China have been helping there! They do all kinds of work or come up with ways to help improve life. Some offer their professional skills for free. Others have no qualifications (资历), but they love to work hard to help.

One of the most famous volunteers in the world was Mother Teresa. She could be the best volunteer because she gave her life to helping the poorest people of Calcutta. She helped the homeless, cared for the sick, gave out food, and became the mother of those without families.

Now more and more teenagers actively look for volunteering opportunities, too. They volunteer because they think it will be fun or they will learn something. They also like the idea of being helpful to others, even if it is just handing out books for the teacher. As they get older, these reasons are still the same, but there are other important reasons for volunteering such as learning on-the-job, getting work experience, and improving their social life.

All volunteers bring joy to the people they help in so many ways. They might read books to the blind, fix up broken homes, find ways to get water for villages. Could you be a volunteer? What kind of volunteer work could you do? There is someone in the world who needs you.

小题1:The Peace Corps is __ in the United States.

A．a city

B．an organization

C．a volunteer

D．a school小题2:The word those in the passage means __ .

A．the homeless

B．the sick

C．the poor

D．the kids小题3:What is NOT the reason for teenagers to be volunteers according to the passage?

A．They want to make more friends.

B．They want to be helpful.

C．It helps them get work experience.

D．It can improve their social life.小题4:Which of the following is true according to the passage?

A．Volunteers need qualifications.

B．Volunteers offer their help without any pay.

C．Young kids can’t be volunteers.

D．Some volunteers bring joy to others.小题5:What is the main idea of this passage?

A．The world needs volunteers.

B．Mother Teresa was a great volunteer.

C．Volunteers do all kinds of work.

D．There are different ways of volunteering.

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实验题

某校化学研究性学习小组的同学对一瓶敞口放置的氢氧化钠产生了兴趣，甲乙两组同学围绕这瓶氢氧化钠进行了一系列的探究活动。

【提出问题】①氢氧化钠是否完全变质②样品中碳酸钠的质量分数是多少?

【查阅资料】①氢氧化钠与二氧化碳反应生成碳酸钠和水

②向氢氧化钠和碳酸钠混合物中加入盐酸时，盐酸先与氢氧化钠反应，再与碳酸钠反应；

【设计实验】实验一：探究氢氧化钠固体的变质情况

①取少量该固体样品置于试管中，向其中加入稀盐酸，发现有气泡产生，说明该样品中含有碳酸钠，由此可确定该固体已发生变质。则反应方程式为。

②为探究该固体中是否还有未变质的氢氧化钠，同学们又进行了如下表所示的实验。请将下表填写完整。

取少量该固体样品溶于水配成溶液，滴加适量的氯化钙溶液，

充分反应后过滤

【设计方案】

①甲组同学：称取16．40g样品，放入过量的盐酸直到反应停止，共收集到4．40g二氧化碳。(设计思路：根据样品与盐酸反应生成二氧化碳的质量求出碳酸钠的质量，再计算样品中碳酸钠的质量分数。)

②乙组同学：称取16．40g样品，加水配成溶液，向溶液中加入过量的澄清石灰水。过滤、洗涤、干燥，共得到白色沉淀10．00g。(设计思路：根据样品与石灰水反应生成沉淀碳酸钙的质量，先求出碳酸钠的质量，再计算样品中碳酸钠的质量分数。)

【解决问题】根据两组同学的实验结果，请你帮助他们计算出样品中碳酸钠的质量分数：_______。（任选一组数据进行计算，写出过程）

【交流与反思】

（1）在交流时，老师问同学们“能否用上述实验所得的数据计算出样品中氢氧化钠的质量分数”，甲乙两组的同学都一致认为可以。但小明思考后，觉得甲、乙两种方案都不妥，理由是：

小明又重新设计新方案：先用电子秤准确称取16.40g变质的NaOH样品放入锥形瓶中，用电子秤秤得锥形瓶及样品的总质量为51.40g，再把175.00g 7.3％稀盐酸平均分成7份依次加入样品中，每次充分反应用电子秤秤得锥形瓶及所盛物质的质量，实验数据记录如下：

加入盐酸的次数	第一次	第二次	第三次	第四次	第五次	第六次	第七次
锥形瓶及所盛物质的总质量	76.40	101.40	126.40	151.40	174.20	197.00	222.00

（2）请根据上述实验数据，计算样品中氢氧化钠的质量分数为_________。（不要写出计算过程)

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