（1）The temperature will stay above zero in the day-time, but at night it will fall below zero again. In the Northwest, there will be snow in the night.
(2) The temperature has dropped.
上面的 fall 与 drop 能否互换？它们有什么区别？
在表示价格或温度下降时 drop 和 fall 可以互换：
The temperature dropped(fell) to zero the next morning. 第二天早晨温度降到零度。但是，在其他方面它们有不少的差别：
A. fall 只能用作不及物动词, 而 drop 既可用作及物动词, 又可用作不及物动词:
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He slipped on the ice and fell. 他在冰上滑倒了。
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Prices have fallen again. 又减价了。
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The fruit dropped from the tree. 果子从树上掉了下来。
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The cheque dropped to the floor. 支票落到了地板上。
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Then the Class 2 runner dropped his stick on the ground. 然后,二班接力赛运动员的接力棒掉在地上。
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He dropped the coffee cup and broke it. (全国高考,93-38) 他的咖啡杯掉在地上,摔碎了。
B. 当表动物的名词作主语时,不及物动词 drop 表示有意志的行为,而 fall 只能表示非意志的的意外动作:
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A burglar dropped from a window to the ground. 一个人室盗窃者从窗口跳到了地上。
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She slipped and fell(down). 她滑倒了。
She ____ the cups and some of them broke.