问题 选择题

下列有关实验现象的描述,正确的是(  )

A.铁丝在氧气中剧烈燃烧、火星四射、生成白色固体

B.分别点燃一小块棉纤维和羊毛纤维,都产生了烧焦羽毛的气味

C.测定空气中氧气含量的实验里,铜丝加热变黑

D.木炭燃烧生成二氧化碳

答案

答案:C

题目分析:
选项A铁丝在氧气中剧烈燃烧、火星四射、生成“白色”固体,应为“黑色”,实验现象的描述错误,故A错误;
选项B分别点燃一小块棉纤维和羊毛纤维,“都”产生了烧焦羽毛的气味,棉纤维燃烧无味,故B错误;
选项C测定空气中氧气含量的实验里,铜丝加热变黑,实验现象的描述正确,故C正确;
选项D木炭燃烧生成二氧化碳,为结论而非现象,故D错误。
故选:C.
阅读理解

Mark Twain was famous in his days as a public speaker. In his public speeches he always liked to tell funny stories. He also liked to listen to funny stories and play jokes on his friends.

One day one of his friends lost his wallet and asked Mark Twain to pay his train fare (车费)for him.

“But I don’t have enough money to pay both your fare and mine, ”Mark Twain said. The friend didn’t know what to do.

“We can do this, ”said Mark Twain. “We can get on the train and when the conductor(列车员) comes to check the tickets,you can hide(藏) under my seat. ”

Later, however, when the conductor came to check the tickets, Mark Twain gave him two tickets-one for his friend and one for himself . Then he explained in a loud voice. “My friend here is a strange man. When he travels on a train, he doesn’t like to sit on the seat. He prefers (宁愿)to lie on the floor under the seat. ”Of course everybody in the train looked at the poor friend and laughed at him loudly.

小题1:Mark Twain told him he couldn’t buy him a ticket because ______.

A.he didn’t have enough money

B.he wanted to play a joke(玩笑) on him

C.he wanted to save some money

D.he didn’t find his wallet, either小题2:When the conductor came to check the tickets, the friend was ________. 

A.lying under the seat

B.sitting on the seat

C.lying on the seat

D.standing nearby小题3:Mark Twain spoke in a loud voice because ______.

A.the conductor was standing far away

B.his friend was deaf (聋)

C.he enjoyed doing so

D.he wanted all the people here to know there was a man under the seat

不定项选择