Why do people wear watches when they cross the desert?

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　　1、What is it that is not burnt in the fire, and can't be drowned in the water?

　　2、I tell heat, and I tell cold, and they in turn tell me to go up and down as I am told. What am I?

　　3、Why do people wear watches when they cross the desert?

　　答案：

　　1、Ice.

　　2、The mercury in a thermomether.

　　3、Because watches have springs in them.