四、在现在时态句里，用情态动词(Modal Verb)的过去时态

　　(could,might,should,would)表示说话人的谦虚、客气、有礼、委婉等：

1. Would you be kind enough to show me the way to the post office.

　　(情态动词 would,表示客气有礼)

2. It would be better for you not to stay up too late.(表示委婉)