怎样区分keep,remain,stay的用法?

stay、remain和keep辨析
1．表示“继续呆在某处”时,应该用不及物动词remain或stay,例如：
Shall I go or stay?
Stay indoors for a few days until you recover from your cold.
He remained in his seat after all the other students had gone home.
2．表示“暂住、短期停留”时,只能用不及物动词stay.例如：
He is staying at Hilton Hotel.
My mother-in-law stayed with us this week when she visited us.
3．表示“残留、剩下”时,只能用不及物动词remain,例如：
Not much of the house remained after the fire.
Of the seven brothers,only four now remain; the rest are dead.
4．表示“继续保持或处于某种状态”时,应视具体情况在上述动词中进行选择：
(1)表示“继续保持或处于原来的状态”时,可用remain或stay,例如：
Three of them remained single.Shops should remain open till later in the evening.
The door stayed closed.But the police themselves prefer to stay unarmed.
(2)表示“需要设法才能保持或处于某种状态”时,应用keep,例如：
She knew she must keep calm.I wish those children would keep quiet.
Although they have many difficulties,they keep happy.
Paul managed to keep awake by drinking lots of strong black coffee.
(3)表示“使某人或某物保持某种状态”时,只能用及物动词keep,例如：
She had kept him waiting twenty minutes on this occasion.
Why do you always keep your windows closed?