维生素D的主要功能是（） A.调节钙、磷浓度，维持正常骨骼 B.

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问题单项选择题

维生素D的主要功能是（）

A.调节钙、磷浓度，维持正常骨骼

B.调节钙、磷浓度，抗氧化

C.维持正常骨骼，保持红细胞完整性

D.维持正常骨骼和上皮组织健全

答案

参考答案：A

填空题

用must, mustn't, can, can't填空。

1. Don't open your present now! In China you _____ wait and open it later.

2. —Can I do cleaning at Spring Festival?

—No, you_____ .

—It's bad luck.

3. In America you _____ open your present immediately.

You don't have to wait!

4. In Britain you _____ ride your bicycle on the pavement _____. It's too dangerous.

5. In Britain, you _____ be 18 if you want to drive a car.

单项选择题

人的全面发展的重要途径是（）

A.生产劳动

B.社会实践

C.教育

D.体脑结合