设随机变量 X的分布函数为 F（x）＝则当 x＞0 时，X的概率密度 f （x）＝_________.

各国有关商事的国内立法不能作为国际商法的渊源。()

Managers set _____and decide how their company can achieve them.

As we are ____ the market for Table cloth, we should be glad if you would send us your best quotation。

We take the liberty____writing to you with a hope to get your best offers for Chinese bicycles.