1.leave…up to somebody
We’ll have to leave the decision up to him.
2. letter of recommendation 推荐信;letter of reference 推荐信
3. look on the bright sides of things 看事物的光明面
4. no kidding 不是开玩笑吧
5.on the tip of one’s tongue 就在舌尖
A: Are you sure you can’t remember the name of that record?
B: It’s just on the tip of my tongue!