You'll fair your next exam unless you start to work hard at

You'll fail your next exam unless you start to work hard at your studies now.为什么是unless?------因为unless== if- - -not == You'll fail your next exam IF you DON'T start to work hard at your studies now.The party ended up with a beautiful song.为什么是ended up?-----因为 ended up == came to an end (结束,解散)