问题 选择题

下图所示装置可用于测定空气中氧气的含量,实验前在集气瓶内加入少量水,并做上记号.下列说法中不正确的是(  )

A.该实验证明空气中氧气的含量约占

1
5
,空气是混合物

B.实验时红磷一定要过量

C.插入燃烧匙时不能过慢,否则反应停止装置冷却到室温后打开弹簧夹上升水面要大于

1
5

D.红磷燃烧产生大量的白雾,火焰熄灭装置冷却到室温后才能打开弹簧夹

答案

A、结合课本相关知识可知,测定空气中氧气含量实验的结论是氧气约占空气体积的

1
5
,所以A正确.

B、红磷过量,能把氧气全部耗尽,实验结论精确.所以B正确.

C、插入燃烧匙时不能过慢,否则里边的空气受热膨胀,反应停止装置冷却到室温后打开弹簧夹上升水面要大于

1
5
,所以C正确.

D、红磷燃烧的现象应是大量的白烟,不是白雾,所以D不正确.

故选D.

单项选择题
阅读理解

John, a famous musician, took his priceless antique violin and played it in the crowded subway station. The music from the violin was delicately streaming throughout the whole station. However, during the one-hour play, only six or seven people were truly appreciating the charming music. A three-year-old kid was so fascinated by the music that he forgot everything around. John only got 52 dollars for his work that day.

However, in normal days, when John is about to hold a concert, one ticket can be sold at more than 100 dollars and it is extremely hard to buy a ticket even at such a high price. Therefore, later, many passers-by in the station that day felt deeply regretful for not recognizing the famous musician and missing such a valuable but cheap music feast.

I have a very busy friend who had totally changed after knowing that his wife came down with incurable illness. He cooked by himself for the family and took a walk with his wife every day. Nonetheless, his wife still did not manage to conquer the illness and passed away after three months. After that, he often sighed miserably that due to his past busy life, he had missed a lot of beautiful time with his wife. But now, it is impossible to make up for it.

It is no use crying over spilt milk. We have missed a lot of precious things in our life without knowing to cherish them.

Actually, I also missed something precious before. The reason why we would have missed those precious things is less than simple: we had thought that we could still own them tomorrow.

Nevertheless, tomorrow is actually by no means reliable. There was a famous Buddhist monk saying that in many people’s lives, they have only done two things: waiting and regretting. The result is that they were always too late to cherish what they had before they lost it. We would often claim to do something when we grow up, or when we have money or when we become old, etc. However, when we reach the condition we have expected, we could no longer realize our wish, because we have lost it by then.

小题1:The reason why people often regret may be that _______.

A.they are too busy to notice the beautiful things

B.they are too careless to cherish precious things

C.they are lazy to observe the surroundings

D.they think that it’s none of their business小题2:The idea the author would like to get across to us seems that _______.

A.actions speak louder than words

B.a bad beginning makes a bad ending

C.the lost will never come back

D.each day brings its own bread小题3:What method does the author employ to support his opinion?

A.By listing data.

B.By comparing the details .

C.By explaining the procedures .

D.By taking examples.小题4:How do we understand the underlined parts “waiting and regretting”?

A.Many people will not cherish what they have until they lost them.

B.Many people cannot do well until they get older.

C.Many people know what they are doing.

D.Many people regret for what they don’t possess.