7.an accident waiting to happen必然会发生的事故；迟早会发生的意外
A lot of the city's older buildings are accidents waiting to happen.城里的许多老建筑迟早都会出问题。
Children treat the road as a playground. It's an accident waiting to happen.孩子们拿马路当运动场, 这样迟早会出事儿。
8.by accident
(not deliberately)无意地
He knocked over the jug by accident.他无意中碰倒了罐子。
The burglar killed him by accident.入室窃贼失手杀死了他。
(by chance)偶然地；意外地
I only came to Liverpool by accident.我只是偶尔来利物浦一次。
She discovered the problem by accident.她意外发现了这个问题。