k out =finish up 把事情做完
le down 专心做一件事情
例句：
Jenny:You wanna go see the new Batman movie?
詹妮：你想去看新上映的蝙蝠侠电影么？
Serena: I can't. I gotta knock out this paper by 10 p.m.
赛琳娜：去不了呢。晚上10点前我得把论文写完。
Jenny: When will you finish up? We can go see the late showing.
詹妮：那你什么时候才能写完呢？我们可以去看夜场。
Serena: I don't know. Just let me buckle down for a few hours.
赛琳娜：我也不知道，让我先好好写几个小时吧。
