一意孤行 That boy is always going his own way. He won't listen to his parents' advice.
一落千丈 My son's schoolwork has gone to pot. He really lets me down.
一鸣惊人 His performance at school really comes as a bombshell.
一诺千金 He never goes back on his word. He is as good as his word.
一时兴起 Don't always do things by fits and snatches.
一蹴可及 You should know that it is impossible to make it at one stroke.
一筹莫展 I really have no idea what to do. Now I am at my wit's end.
一览无遗 If you stand here looking down at the city. The wonderful scene will be in full view.
一窍不通 What you said is all Greek to me.
小Car笔记：
wit's end:技穷