1children like to watch TV. It' s very 2. On TV3can see and learn a lot and know many things 4 their country and the world.5they can learn over the radio. But they can learn better and more easily on6.Why? Because they can hear and watch at the same time. But they can' t 7 anything over the radio.

    Many children watch TV only on Saturday or Sunday evening.They are 8 busy with their lessons. But a few children watch TV every 9. They go to bed very late. They can' t have a good10. How about you, my young friend?

如图，在一个标准大气压下，某同学将冰块放入空易拉罐中并加入适量的盐，用筷子搅拌大约半分钟，测得易拉罐中冰与盐水混合物的温度低于0℃，实验时易拉罐的底部有白霜生成．对于这一实验和现象的分析，正确的是（  ）

当你看到一张男孩的照片，想知道他是不是Zhang Hua的弟弟时，你应该问Zhang Hua：(       )

如图，AB是⊙O的直径，⊙O的半径$\sqrt{3}$cm，弦CD⊥AB于E，∠CDB=30°，则弦CD的长为（　　）

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