如何用英文正确表述“我不知道”？

英语和汉语一样，是一门语言。

也有一个单词几种或多种表达方式。

我不知道在英译里有这几种表达方式：一、I don't know例句：我不知道发生了什么事。

I don't know what's going on.二、I have no idea.例句：I have no idea what I should to next. 我不知道下一步怎么办？三、I don't understand.I don't understand What you said .我不知道你说的话。

四、I am afraid.例句：I am afraid it's too late.恐怕天太晚了。

五、who knows?例句：who know What has happened ?谁知道发生了什么事呢?

-You have me completely stumped 我怔住了- I genuinley have no idea 我真不知道- I could talk for day's about (different topic)我不知道 ：i have no idea我完全不知道 : i have absolutely no idea但我觉得 : but my best guess isWell, you have me completely stumped! I genuinley have no idea. If you asked me about sports, I could talk for day's about sport, if you asked me about music, I could talk for hours about music . but international law? I have no idea, sorry.