允许: 询问或说明一件事可不可以做.
May I trouble you with a question?
You may take this seat if you like.
He asked if he might glance through my album.
You might as well speak your mind.
可能: 表示一件事或许发生.
You may walk ten miles without seeing a house.
She was afraid they might not like the idea.
A bad thing might be turned to good account.
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