you could do 与 you can do 有啥区别

what can i do for you与 can i help you的回答有什么区别? can you；could you有什么区别? Can you speak English 与 Do you speak English 有什么区别 Can you speak English?与Do you speak English?在用法上有什么区别吗 you could do worse YES,AND YOU CAN SURE YOU COULD DO IT could you tell me .what can I do for you how can you do that & how did you do that 有什么区别 can you have you are you do you 在什么情况下提问? 有什么区别? are you与do you的区别? do you 与are you 的区别 are you 与 do you 的区别