clue

如果你不给我一点提示，我永远猜不到答案。

I'm never going to guess the answer if you don't give me a ___clue.

这个指纹是破案的重要线索。

The fingerprint is a crucial ___clue to solving the case.

他正努力寻找破案的关键线索。

He is trying hard to find the key ___clue to solve the case.