英语语气提问why don't you tell us about thatcan you tell us about thatcould you tell us about that 以上三句话的语气 区别

英语语气提问
why don't you tell us about that
can  you tell us about that
could you tell us about that 
以上三句话的语气 区别

第一句：你为什么不告诉我们关于那件事?是质疑的语气.
第二句：你能告诉我关于那件事吗?是疑问语气.
第三句：你可以告诉我关于那件事吗?是很委婉的语气.

why don't you tell us about that
质问的语气
can you tell us about that
普通疑问语气
could you tell us about that
委婉的语气

1、你为什么不告诉我们呢 质疑
2、你能告诉我们关于这 疑问
3、你能告诉我们关于 委婉