211.be on duty 值班,值日,在上班时
212.be in duty bound to 有义务(做)
213.be eager for 想得到,盼望
214.by ear 凭记忆,不看乐谱
215.have an ear for 对有鉴赏力
216.a word in one's ear 私房话,秘密话
217.on earth到底,到底,全然
218.with ease 容易,不费力
219.at ease 自在,不拘束
220.put sb. at his / her ease 使某人感到无拘束
221.economize1 on 节省
222.have an effect on 对有影响
223.be in effect 有效
224.go into effect 生效。
225.in effect 事实上