at one's fingertips　了如指掌

How to get at that little island is at his fingertips.他知道怎么去那个小岛。

at one's wit's end　智穷

Don't ask him.It is also at his wit's end.不要问他了，他也不知道。

big shot 大人物，大亨

He is a big shot in our little town.

black sheep　败家子，害群之马

Every family has a black sheep.家家有本难念的经。

black and blue　遍体鳞伤

The thief was caught of red-handed and beaten black and blue.那个小偷当场被抓住并被打得青一块紫一块的。

black and white　白纸黑字

The proof is in black and white and the murderer has no any excuses.证据确凿，凶手再也无话可说。