问题 填空题

为防止燃气泄漏造成危险,可在家中安装报警器,当报警器接触到一定量的泄漏气体时,会发出响声.有位同学家中所使用的燃料是天然气,试判断报警器安装的位置应为图______(填“A”或“B”)所示,简述你的判断理由:______.

答案

天然气的密度小于空气的密度,泄漏后会很快上升到室内的上方,接触报警器,因此报警器应安装在房间内墙上方的位置(A处).

故答案为:A;天然气的密度比空气小.

填空题

阅读下面的短文,用括号中所给动词的适当形式填空,必要时可加助动词。

     You may know the song Happy Birthday very well. But do you know about its writer? It was written by an

American girl. And now she 1.             (become) a very rich woman. 

     When she was a child,she was poor. Once she 2.             (invite) to her friends' birthday party. She was

very pleased but sad because she had not enough money to buy presents for them. "The party 3.             (come)

soon. Now I have little money." Tears ran down her face.

     Later that night she was in bed, thinking about the presents when the door opened and in came her grandma,

"What 4.             (happen)?" her grandma asked. Hearing the girl's story, she said, "5.             (not worry), I

think I 6.             (help) you. How about singing a song together? Happy birthday to…" What a beautiful song!

They sang and sang. Suddenly she woke up. It was a dream! She decided to write it down at once and 7.          

(sing) it to her friends at the party.

     When she sang the song at the party the next day, her little friends were very happy. "How wonderfully she

8.            (sing)! We 9.             (not hear) such a song before. Thank you for 10.             (give) us the special

present." said one of them. And they learnt to sing it together. Later the girl became well known in America.

单项选择题