改错An apple a day keep the doctor away.答案上是把keep改成keeps,为什么啊?

改错An apple a day keep the doctor away.答案上是把keep改成keeps,为什么啊? 是An apple a day keep the doctor away.还是An apple a day keeps 每天一个苹果,医生远离你的英语,是An apple a day ,keeps the doctor away还是keep eat a apple a day keeps the doctor away.为什么不用to keep表目的 An Apple a day might keep the doctor away? An apple a day,keep the doctor away. An apple a day ______(keep)the doctor away. An apple a day ,keep the doctor away! an apple a day ,keep the doctor away. an apple a day keep the doctor away 怎么翻译? An apple a day keeps the doctor away .中的Keeps为什么要加S? An apple a day keeps the doctor away.为什么不用one apple