单项选择题

While air is in the lungs, it changes in the following way: ______.

A．Nitrogen is absorbed from the air
B．About one-fifth of the carbon dioxide and about one-half of the oxygen in the air goes into the blood
C．The moisture in the air is almost completely evaporated
D．About one-fifth of the oxygen in the air goes into the blood and an equivalent amount of carbon dioxide enters the air from the blood
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单项选择题
In the respiratory process, the following action takes place: ______.
A．Diffusion of blood through capillary walls into air sacs
B．Exchange of alveoli and oxygen within air sacs
C．Diffusion of oxygen through the air sac and capillary walls into the blood
D．None of the above
单项选择题
In the passage, we can find the author was ______
A．quite satisfied with her life
B．a poor Jewish girl
C．born in a middle-class family
D．a resident in a rich area in New York
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