为什么不说中文？
英文翻译：
Why not speak Chinese?
Why don't you speak Chinese?
Could you speak Chinese?
重点词汇解释：
why
used in questions to ask the reason for or purpose of sth
（用于问句）为什么，为何
speak
(not used in the progressive tenses 不用于进行时) to be able to use a particular language
会说，会讲（某种语言）
could
used to politely ask sb to do sth for you
（礼貌地请求别人做事）能，可以
