1.I don't have a clue.我一无所知
Could you please give me at least a clue?
Could you please give me some clue?
2.I'm clueless .我一无所知
3.I don't have the faintest idea.
faint vi.晕倒 adj.微弱的虚弱的渺茫的
a faint smell 一种微弱的气味
a faint smile 一个淡淡的微笑
I have no idea at all.
4.I don't have the vaguest notion.
notion n.观念 概念（来自拉丁语）
以"gue"结尾的词，来自法语
vogue n.时尚
vague adj.模糊的， 不确定的（凡是gue结尾的词都是来自法语的，都不能完全按英语的发音）
5.How should I know?
我怎么会知道呀（可以用来怼回别人）