My turtle fell behind a radiator and was not discovered until too late.

我的龟掉到一个散热器的后面，发现时已经太晚了。

She soon fell behind the leaders.

她很快就落在领先者的后面。

Soon he fell behind in the race.

很快他在赛跑中落在了后面。

So he fell behind in his studies.

于是他学习落后了。

Smith fell behind in the race.

史密斯在赛跑中落后了。