题目

In bringing up children，every parent watches eagerly the child’s acquisition（学会）of each new skill—the first spoken words，the first independent steps，or the beginning of reading and writing．It is often tempting to hurry the child beyond his natural learning rate，but this can set up dangerous feelings of failure and states of worry in the child．This might happen at any stage．A baby might be forced to use a toilet too early，a young child might be encouraged to learn to read before he knows the meaning of the words he reads．On the other hand， though， if a child is白磷是一种能在空气中自燃的物质，请你利用物质燃烧与燃烧的条件和灭火的原理，分析实验室里，少量的白磷为什么必须保存在冷水中？