七年级英语单词中前面需要加an的单词有哪些,50个以上······

eye, hour, umbrella, elephant, apple, angle, American, island, an old man, orange, answer, idea, actor/ actress(男/女演员）, engineer(工程师）, inventor（发明家）, airplain, industry(工厂）, agreement(协议）, artical, office, event, understanding, age, opinion,enemy(敌人）, address(演说）, apartment(公寓）, 18(eighteen), accident, orphan（孤儿）, assistant(助手）, apology(道歉）, emergency(突发事件）, explanation（解释）, an interesting/exciting story(一有趣/令人兴奋的故事）, excellent(优秀的）, honor（荣幸）, excuse(借口）