问题 选择题

下列实验操作及现象合理的是                                       

A.用50 mL量筒量取5.26 mL水

B.铁丝在氧气中燃烧,发出白光,产生白色固体

C.用托盘天平称取5.6 g 硝酸钾固体

D.燃着的镁条伸到充满CO2的集气瓶中,镁条熄灭

答案

答案:C

A、选取量筒时要选择比所量体积的数值大,且最接近它的那个量程的量筒,量取5.26mL水,要用10mL量筒,故A错误;

B、铁丝燃烧的现象是:剧烈燃烧、火星四射、生成黑色固体、放出热量,故B错误;

C、因为托盘天平能准确到0.1g,用托盘天平能称取5.6g硝酸钾固体,故C正确;

D、由于镁条在CO2的集气瓶中能够燃烧,所以将燃着的镁条伸到充满CO2的集气瓶中,镁条不会熄灭;故D错误.

故选C

填空题
阅读理解

It was a village in India. The people were poor. However, they were not unhappy. After all, their forefathers had lived in the same way for centuries.

Then one day. Some visitors from the city arrived. They told the villagers there were some people elsewhere who liked to eat frog’s legs. However, they did not have enough frogs of their own, and so they wanted to buy frogs from other places.

This seemed like money for nothing. There were millions of frogs in the fields around, and they were no use to the villagers. All they had to do was catch them. Agreement was reached, and the children were sent into the fields to catch frogs. Every week a truck arrived to collect the catch and hand over the money. For the first time, the people were able to dream of a better future. But the dream didn’t last long.    

The change was hardly noticed at first, but it seemed as if the crops were not doing so well. More worrying was that the children fell ill more often, and, there seemed to be more insects around lately.

The villagers decided that they couldn’t just wait to see the crops failing and the children getting weak. They would have to use the money earned to buy pesticides(杀虫剂) and medicines. Soon there was no money left.

Then the people realized what was happening. It was the frog. They hadn’t been useless. They had been doing an important job---eating insects. Now with so many frogs killed, the insects were increasing more rapidly. They were damaging the crops and spreading diseases.

Now, the people are still poor. But in the evenings they sit in the village square and listen to the sounds of insects and frogs. These sounds of the night now have a much deeper meaning.

小题1:From paragraph I we learn that the villagers __________.

A.worked very hard for centuries

B.dreamed of having a better life

C.were poor but somewhat content

D.lived a different life from their forefathers小题2:Why did the villagers agree to sell frogs?

A.the frogs were easy money

B.They needs money to buy medicine

C.they wanted to please the visitors

D.the frogs made too much noise小题3: What might be the cause of the children’s sickness?

A.the crops didn’t do well

B.there were too many insects

C.the visits brought in diseases

D.the pesticides were overused小题4:What can we infer from the last sentence of the text?

A.Happiness comes from peaceful life in the country

B.Health is more important than money

C.The harmony between man and nature is important

D.good old day will never be forgotten