You have learned that dissolved materials always diffuse from where there is more of them to where there is less. Oxygen from the air dissolves in the moisture on the lining of the air sac and diffuses through the lining into the blood. Meanwhile, carbon dioxide diffuses from the blood into the air sac. The blood then flows from the lungs back to the heart, which sends it out to all other parts of the body. Soon after air goes into an air sac, it gives up some of its oxygen and takes in some carbon dioxide from the blood. To keep diffusion going as it should, this carbon dioxide must be gotten rid of. Breathing, which is caused by movements of the chest, forces the used air out of the air sacs in your lungs and brings in fresh air. The breathing muscles are controlled automatically so that you breathe at the proper rate to keep your air sacs supplied with fresh air. Ordinarily, you breathe about twenty-two times a minute. Of course, you breathe faster when you are exercising and slower when you are resting. Fresh air is brought into your lungs when you breathe in, or inhale, while used air is forced out of your lungs when you breathe out, or exhale. 26. In the respiratory process, only one of the following actions takes place: it is_______. A. the diffusion of blood through capillary walls into air sacs B. the diffusion of carbon dioxide through capillary and air sac walls into the blood C. the diffusion of oxygen through the air sac and capillary walls into the blood D. the exchange of nitrogen within air sacs 27. The number of times per minute that you breathe is_______. A. independent of your rate of exercise B. fixed at twenty-two times per minute C. influenced by your age and sex D. controlled automatically by an unspecified body mechanism 28. The process by which carbon dioxide and oxygen are transferred does not depend on A. the presence of nitrogen in the blood B. breathing muscles C. the flow of blood D. the moisture in the air sac linings 29. The authors style in this passage can best be described as---------. A informal and matter of fact B. impersonal C. personal P- matter of fact and formal 30. Which of the following words can replace the word exhale? A. Breathe out. B. Breathe in. C. Diffuse. D. Exchange.
双语儿童寓言故事:晒冰Sun the Ice
双语儿童寓言故事:两只猴子Two Little Monkeys
双语儿童寓言故事:漂亮的洋娃娃A Beautiful Doll
儿童双语幽默小故事:可怜的乔治Poor George
儿童双语幽默小故事:狼与鹤The Wolf and the Crane
儿童双语幽默小故事:狼来了Wolf Is Coming
儿童双语幽默小故事:我没法煮它I can’t Cook It
双语儿童寓言故事:一个愚蠢的人 A Silly Man
儿童双语幽默小故事:去电影院Go to the Cinema
双语儿童寓言故事:聪明的机器人Smart Robot
儿童双语幽默小故事:一只口渴的狗The Thirsty Dog
双语儿童寓言故事:顽皮的弟弟Naughty Brother
梦想: Dreams
双语儿童寓言故事:聪明的农民A Clever Farmer
儿童双语幽默小故事:一只蚂蚁A Little Ant
双语儿童寓言故事:我的“公鸡”闹钟My “Cock” Clock
双语儿童寓言故事:我不能愿意洗澡I Will Not Take a Bath
儿童双语幽默小故事:一定很拥挤It Must Be Crowded
双语儿童寓言故事:我与河马The Hippo and I
双语儿童寓言故事:穿哪条裙子?Which Skirt to Wear?
儿童双语幽默小故事:聪明的国王所罗门The Clever King Solomon
双语儿童寓言故事:两只狗Two dogs
儿童双语幽默小故事:渔夫和他的妻子The Fisherman and His Wife
儿童双语幽默小故事:兔子和狐狸The Rabbit and the Fox
双语儿童寓言故事:男孩和猴子A Boy and a Monkey
儿童双语幽默小故事:聪明的乌龟A Smart Tortoise
儿童双语幽默小故事:牛和狗The Ox and the Dog
双语儿童寓言故事:动物Animals
儿童双语幽默小故事:白雪公主Snow White
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