请给我冠词用an的英语单词答:总的原则:元音音标前用an,辅音音标前用a。(Go for it)初一用an的单词有:apple, orange, egg, eraser, English girl, answer, aunt, example, interesting book, old man, article, animal, assistant, airport,uncle, elephant, exam, expensibe car, ugly man, unfriendly boy ...