An apple a day keeps the doctor away为什么doctor不加s

an apple a day keeps the doctor 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 翻译:an apple a day keeps the doctor away.'' 英语翻译:eat an apple a day keeps the doctor away. An apple a day keeps the doctor away An apple a day keeps the doctor away 啥意思 Eat an apple a day keeps the doctor away. An apple a day keeps the doctor away. An apple a day keeps the doctor away. An apple a day keeps the doctor away. an apple a day keeps doctors away 出自哪 翻译：An apple a day keeps the doctors away. An apple a day keeps the docter away. an apple a day keeps the doctor away的意思 关于an apple a day,keeps the doctor away到底是an apple a day an apple one dayone apple a day还是one apple one day An apple a day keeps the doctor away .中的Keeps为什么要加S? An apple a apple要解释为苹果吗原句是An apple a day keeps the doctor away.