311. in fear of (=afraid for the safety of) 担心
312. feed (sb.) on sth. 靠吃…, 用…喂养
313. be fed up with(=be unhappy, tired about sth. dull) 厌烦, 腻了
314. feel like (=have a desire for) 想要
315. fill in 填写
316. fill out ( =fill in )填写
317. set the world on fire=set the flames on fire(=do sth. remarkable)有突出成就
318. play with fire (=take great risks)干冒险事
319. set sth. on fire(=set fire to sth.)使..着火,放火
320. at first sight(=when first seen)乍一看,一见