211．be on duty 值班，值日，在上班时
212．be in duty bound to (do) (=be required by one's job or esp. by conscience) 有义务（做）
213．be eager for 想得到，盼望
214．by ear (=play music from memory without having seen it printed) 凭记忆，不看乐谱
215．have an ear for (=have keen recognition of sounds esp. in music and language.) 对……有鉴赏力
216．a word in one's ear 私房话，秘密话
217．on earth究竟，到底，全然
218．with ease (=easily) 容易，不费力
219．at (one's) ease ( = without worry or nervousness) 自在，不拘束
220．put sb. at his / her ease (=free sb. from worry or nervousness) 使某人感到无拘束
221．economize on (=save sth. instead of being wasteful) 节省
222．have an effect on 对……有影响
223．be in effect (=be in operation) 有效
224．go into effect 生效。(近：come into effect; take effect; be brought into effect)
225．in effect (=in fact, really) 实际上