问题 选择题

下列物质的应用正确的是(    )

A

答案

答案:A

A、天然气的主要成分是甲烷,甲烷易燃烧,常用作燃料,故A正确;

B、利用铁的导电性,但是由于铁的电阻太大,所以通常不用铁做导线,故B错误;

C、氧气能够供给呼吸,所以在医疗上氧气用于给病人输氧,而不是麻醉,故C错误;

D、固态的二氧化碳升华时吸热,可用于人工降雨,但是二氧化碳气体不能用于人工降雨,故D错误;

故选A

选择题
阅读理解

Who doesn’t love sitting beside a cosy fire on a cold winter’s night ? Who doesn’t love to watch flames (火苗) curling up a chimney? Fire is one of man’s greatest friends, but also one of his greatest enemies. Many big fires are caused by carelessness. A lighted cigarette thrown out of a car or train window or a broken bottle lying on dry grass can start a fire. Sometimes, though, a fire can start on its own. Wet hay (草) can begin burning by itself. This is how it happens: the hay starts to rot (腐烂) and begins to give off heat which is trapped inside it. Finally, it bursts into flames. That’s why farmers cut and store (贮存) their hay when it’s dry. 

Fires have destroyed whole cities. In the 17th century, a small fire which began in a baker’s shop burnt down nearly every building in London. Moscow was set on fire during the war against Napoleon. This fire continued burning for seven days. And, of course, in 64 A.D. a fire burnt Rome. Even today, in spite of modern fire-fighting methods, fire causes millions of pounds’ worthy of damage each year both in our cities and in the countryside. It has been wisely said that fire is a good servant but a bad master .

39. The writer considers it ________ to sit beside a fire on a cold winter night .

A. nice      B. dangerous      C. unhappy        D. painful

40. Which of the following describes the way how hay begins burning on its own ?

A. wet hay ---- becomes dry ---- gives off heat ---- burns

B. dry hay ---- gets too much heat from the sun ---- gives out heat --- starts to burn

C. wet hay ---- begins to rot ---- gives out heat ---- starts to burn

D. dry hay ---- gives off heat ---- starts to rot ---- starts to burn

41. Many big fires are caused __________ .

A. by cigarette             B. by their own    

C. by dry grass              D. by people’s carelessness

42. How many examples did the writer give to show fires can destroy the whole city ?

A. One      B. Two      C. Three           D. Four

43. Which of the following statement is not true ?

A. Fires still cause much damage now although there are modern fire - fighting methods .

B. Fires cause less damage in the country than in the city .

C. Fire can be man’s good friend and also great enemy .

D. One should be careful not to throw a lighted cigarette everywhere .