Q:____I have an apple?A:sure.Help yourselfA could B should C would D,DO简要说说理由

Q:____I have an apple?A:sure.Help yourself
A could B should C would D,DO
简要说说理由

could
这里是情态动词的用法
should 应该
would 将要
do 助动词

Could 我可以吃个苹果吗？用Could，其他说不过去

could语气委婉，表请求，询问

Could