1.It was one of mother's maxims-never look a gift horse in the mouth.
母亲的箴言之一是对于收到的礼物绝不要挑毛病。
don't look a gift horse in the mouth:
Do not unappreciatively question a gift or handout too closely.
2.Would you stop being a backseat driver? I don't want you to teach me how to drive.
你可不可以不要再指指点点了?我不需要你教我怎么开车。
He is a backseat driver, and he always tells me what to do.
他是个多管闲事的人，总是告诉我该做什么。
back-seat driver:
A person sitting (typically) in the back seat of a car issuing (unsolicited and usually unwanted) instructions to the driver.
(figuratively) An opinionated person who offers (unsolicited and often unwanted) advice on the best way to handle a situation.
3.He is a rubbernecker. You can see him at every quarrel scene.
他特别喜欢看热闹。哪里有吵架，哪里就有他的身影。
rubbernecker:
Someone who watches, a spectator, in the sense that they crane their neck as though it were made of rubber. Especially those who watch accidents.
