为什么是an apple a day而不是a day an apple

是An apple a day keep the doctor away.还是An apple a day keeps an apple a day keeps the doctor An apple a day keeps the doctor away.An apple a day that’s w An apple a day keeps the doctor away.为什么不用one apple an apple a day keeps a doctor away,是什么意思 An apple a day keeps a doctor away是什么意思? 请问为什么苹果和鸡蛋要用,an apple、an egg 而不是a apple、a egg Tom has an apple a day.对an apple 进行提问! An apple a day is good _____ health. 英语翻译:eat an apple a day keeps the doctor away. Eat an apple a day keeps the doctor away. an apple a day keeps doctors away 出自哪