问题 选择题

随着温度和压力的变化,任何一种物质都存在三种状态(气、液、固)。液、气共存状态的点叫临界点。超临界流体是指温度和压力均高于其临界点的流体。超临界CO2流体是一种和水相似,能阻燃、溶解能力强的绿色环保溶剂。下列有关超临界CO2流体的说法错误的是

A.超临界CO2流体不能燃烧

B.是一种无毒溶剂

C.是CO2呈现的一种状态

D.是一种与干冰化学组成不同的物质

答案

答案:D

A、超临界CO2流体,其组成还是二氧化碳,则不能燃烧,故A选项正确;

B、因为超临界CO2流体溶解能力强的绿色环保溶剂,CO2本身无毒,故B选项正确;

C、超临界CO2流体,其组成还是二氧化碳,是CO2呈现的一种状态,故C选项正确;

D、与干冰为不同的形态,但组成一样,所以“是一种与干冰化学组成不同的物质”,故D选项错误;

故选D.

阅读理解

            Being the head of a high school for many years, I grew tired of budget meetings, fundingcuts, and many other administrative chores and started to dream of retirement.Sitting in trafficon a weekday morning, I would find my mind wandering.I would imagine spending time withmy grandchildren, quiet evenings with my wife, traveling, or rediscovering some great books.Itold myself that I wouldn't sign myself up for any committees, any classes, or anythingrequiring a schedule.

My first day of retirement came at last! I cooked a great breakfast for my wife and me,leisurely read the paper, cleaned a bit of the house, and wrote a few letters to friends.On thesecond day, I cooked breakfast, read the paper …On the third day, ...This is retirement? Itried to tell myself that it was just the transition, that those golden moments were right roundthe corner, and that I would enjoy them soon enough.But something was missing.

A former colleague asked a favor.A group of students was going to Jamaica to work withchildren in the poorest neighbourhood.Would I interrupt my newfound "happiness" and returnto the students, just this once? One trip.That's all.My bags were packed and by the door.

The trip was very inspiring.I was moved not only by the poverty I saw but also by thesense of responsibility of the young people on the trip.When I returned home, I offered to workone day a week with a local youth organization.The experience was so positive that I was soonvolunteering nearly full-time, working with students across North America to assist them intheir voluntary work.

Now,it seems, the tables have turned .Some days I am the teacher, other days I am thestudent.These young people have reawakened my commitment to social justice issues bychallenging me to learn more about the situation in the world today, where people are still poorand suffer because of greed, corruption and war.Most importantly, they have given me theopportunity to continue to participate in helping to find solutions.In return, I help them do theircharitable projects overseas.I've gone from running one school to helping oversee theconstruction of schools in twenty-one countries!

小题1:What did the writer expect to do after he retired?

A.To stay away from busy schedules.

B.To write some great books.

C.To do some voluntary work.

D.To plan for his future.小题2:Why did the writer decide to go to Jamaica?

A.He missed his students in that country.

B.He couldn't reflise his colleague's favor.

C.He was concerned about the people there.

D.He was not satisfied with his retired life.小题3:The underlined part "the tables have turned" (Paragraph 5 ) means that thewriter  

A.improved the situation in his school

B.felt happy to work with students again

C.became a learner rather than a teacher

D.changed his attitude toward his retired life小题4:What does the writer think of his retired life now?

A.Disappointing.

B.Troublesome.

C.Promising.

D.Meaningful.

单项选择题