更多"Trains running through Upper Silesi"的相关试题:
[填空题]Trains running through Upper Silesia have to slow their speed because the tracks are very wet and slippery.
[单项选择]The high-speed trains can have a major impact on travel preferences( ).
A. force
B. influence
C. surprise
D. power
[填空题]The factories and coal mines in Upper Silesia produced much more pollution than Ruhr Valley in Germany.
[单项选择]Blood vessels running all through the lungs carry blood to each air sac (囊), or alveolus (肺泡), and then back again to the heart. Only the thin wall of the air sac and the thin wall of a capillary (毛细血管) are between the air and the blood. So oxygen easily diffuses from the air sacs through the walls into the blood, while carbon dioxide easily diffuses from the blood through the walls into the air sacs.
When blood is sent to the lungs by the heart, it has come back from the cells in the rest of the body. So the blood that goes into the wall of an air sac contains much dissolved carbon dioxide but very little oxygen. At the same time, the air that goes into the air sac contains much oxygen but very little carbon dioxide. 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 diff
A. produce energy for breathing
B. diffuse immediately in the blood
C. penetrate slowly into the air sacs
D. travel in opposite ways in the lungs