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【B12】
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Cactuses(仙人掌)live in dry areas. They may not get much water where they live. The cactus' long roots lie near the surface of the ground. They can get water from desert rains. And since the roots have bark (皮)covering them, they can absorb the water fast. Because the cactus has no leaves, it seems to do the job of making food for the plant and of storing it than out, not much of the plant faces the direct drying sunlight. These broad stems have a great deal of room for storing the water and a thick covering for protecting it. The plant's sharp, pointed needles (针) keep animals from sucking its liquid. However, cactus plants have saved the lives of people in the desert.
_________of the cactus take in water.
【B9】
【B3】
Vitamin D is also called the sunshine vitamin. It forms when the skin is exposed to the sun. In the past people Blew what vitamin D was they learned that sunshine was important. Poor children lived in crowded slums (贫民窟). And they were often ill with tickets (软骨病) . In Englad a tax was once placed on windows. Builders put few windows in houses. Rickets became so common that it was called the English disease.
Because adults have reached full growth, they probably__________.
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