Airline staff should always be on the watch for criminal activity.航空公司员工应该时刻提防犯罪活动。When you're driving in winter you should always be on the watch for ice on the roads.冬天开车时，应该时刻注意结冰的路面。Environmentalists will be on the watch for damage to wildlife.环保主义者会密切关注对野生动物造成的伤害。