[译] 第二次世界大战前爱因斯坦得以成功地离开欧洲。
[误] Einstein could leave Europe before the Second World War began.

[正]Einstein was able to leave Europe before the Second World War began.
[注]can 与 be able to 是同义词，有时可以替换使用，如：He couldn’t understand her. 他不能理解她。也可以说：He wasn’t able to understand her. 但是表示一个行动已经顺利完成时须用 be able to，例如：He didn’t agree with me at first but I was able to persuade him. 开始他不同意我的意见，可是我成功地说服了他。