问题 选择题

家鸽飞行时肺内进行气体交换是在什么时候(  )

A.吸气时

B.呼气时

C.吸气和呼气时

D.吸气和呼气之间

答案

家鸽的体内有很多气囊,这些气囊与肺相通.家鸽吸气时,空气进入肺,在肺内进行气体交换,同时一部分空气进入气囊暂时储存;呼气时,气囊中的气体又进入肺,在肺内进行气体交换.这样,家鸽每呼吸一次,气体两次进入肺,在肺内进行两次气体交换,这样的呼吸方式叫做双重呼吸.双重呼吸是鸟类特有的呼吸方式,它大大提高了气体交换的效率.可见C符合题意.

故选:C

阅读理解

阅读理解。

     My son Karl talked little after his father died. As a single parent, I tried to do my best to talk to him. But

the more I tried, the more withdrawn he became. His report card arrived, saying that he had been absent 95

times from classes and failed in the exams. I sent him to the school advisor, and I even begged him. Nothing

worked.

     One day, I was at work when I got a phone call. A man introduced himself as the headmaster. "I want to

talk to you about Karl's absences." Before he could say another word, all my disappointment and sadness over

Karl came pouring out into the ears of this stranger. "I love my son but I just don't know what to do. I've tried

everything to get Karl to go back to school and nothing has worked. It's out of my hands." For a moment there

was silence on the other end of the line. The headmaster seriously said, "Thank you for your time", and hung

up.

     Karl's next report card showed marked (显著的) improvement in his grades. Last week I attended a parent-

teacher meeting with Karl. His teachers praised him a lot and were amazed at the way he had turned himself

around. On our way home, he said, "Mum, remember that call from the headmaster last year?" I nodded. "That

was me. I thought I'd play a joke but when I heard what you said, it really hit me how much I was hurting you.

That's when I knew I had to make you proud."

1. The word "withdrawn" in the first paragraph probably means _____.

A. 好奇

B. 孤僻

C. 害羞

D. 脆弱

2. The phone call the mother got was made by _____.

A. Karl

B. a stranger

C. her husband

D. the headmaster

3. There was silence on the other end of the line because _____.

A. the line was busy at that time

B. something might be wrong With the line

C. the speaker was too moved to say anything

D. the speaker waited for her to finish speaking

4. Karl turned himself around because _____.

A. his teachers asked him to do so

B. he failed many times in the exams

C. he wanted to make his mother proud

D. the headmaster had phoned his mother 

5. What is the main idea of this passage?

A. Children in single-parent families often have problems.

B. Mother's love plays an important role in children's life.

C. Being understood by parents is very important to children.

D. School education doesn't work without support from parents.

单项选择题