留意那辆送货面包车。

___Keep ___an ___eye ___out ___for the delivery van.

我们应该留意病人病情的任何变化。

We should ___keep ___an ___eye ___out ___for any changes in the patient's condition.

警方正在留意该地区的可疑活动。

Police are ___keeping ___an ___eye ___out ___for suspicious activity in the area.