问题 选择题

吸气时,肺容积和气压变化的情况是(  )

A.肺容积增大,气压升高

B.肺容积缩小,气压升高

C.肺容积增大,气压降低

D.肺容积缩小,气压降低

答案

答案:C

吸气时,胸廓容积扩大,外界大气压大于肺内气压。人在平静状态,肋间外肌的收缩时,肋骨上提,胸骨向上向外移动,使胸廓的前后径和左右径都扩大;膈肌收缩时,膈顶部下降,使胸廓的上下径增大;这时候,胸廓扩大,肺随着扩张,肺的容积增大,肺内的气压下降,外界空气就通过呼吸道进入肺,完成吸气动作。故本题选C。。

单项选择题
阅读理解

第三部分:阅读理解(共20小题;每小题2分,满分40分)

第一节:阅读下列短文,从每题所给的四个选项(A、B、C和D)中,选出最佳选项。

Since her husband died, Mrs. Jackson has lived alone in their big old suburban (郊区的) house. The house was bought by her husband almost fifty years ago.

For the sake of safety (为安全起见), her son has tried hard to ask her to sell the house and buy a new and small one in the town. But Mrs. Jackson doesn’t like the idea. She says that she has to look after her husband’s old house. But recently she often hears stories about unknown people stealing things around here.

That was a cold day before Christmas Eve. Around four o’clock in the afternoon, Mrs. Jackson was enjoying the Christmas music when someone knocked at the door. She heard the sound but didn’t move. Another knock. Who could it be? Mrs. Jackson was a bit afraid. She decided not to answer the door but keep waiting.

One minute another minute and yet another minute. Nothing happened and no more knocks. She walked quietly to the door, and listened. She heard nothing but the wind outside. She slowly unfastened the door and peeped (窥视) through the crack (小缝). She then gave a surprised cry and threw the door wide open! At the door she saw a tall, beautiful Christmas tree! In the tree stood a Christmas card with these words:

Merry Christmas!

Your new neighbor

56. The house bought by Mr. Jackson is _____.

A. in the town               B. small but new        C. outside the town        D. small and old

57. Mrs. Jackson doesn’t want to sell the house because _____.

A. it is almost fifty years old                             B. it is big and old

C. she likes to live alone in it                            D. her husband left it to her

58. Why didn’t she move when she heard the knock at the door?

A. Because she was enjoying the Christmas music.

B. Because she thought it might be an unknown person.

C. Because it was not her son.

D. Because she hadn’t decided to answer the door.

59. When she found it was a Christmas tree, she _____.

A. cried in surprise and pushed the door wide open                                       

B. was very excited      

C. threw the door away 

D. went out to stand in the tree