vigilant

警卫时刻保持警惕。

The guard remains ___vigilant.

游泳池挤满了嬉水的孩子，救生员一刻不停地保持警惕。

The lifeguard stayed ___vigilant as dozens of children splashed in the crowded pool.

在收到最近的落石警告后，这位徒步者穿越狭窄山道时始终保持警惕。

The hiker remained ___vigilant while crossing the narrow mountain trail after a recent rockslide warning.