工人们正在检查船的龙骨以确保航行安全。

The workers are inspecting the ship's ___keels to ensure sailing safety.

强风使小船突然倾覆了。

The strong wind made the small boat ___keel over suddenly.

这位老人在烈日下站得太久，突然晕倒了。

The old man stood too long in the scorching sun and suddenly ___keeled over.