industrious: 勤劳的，勤奋的。如：He is an industrious student.(他是个用功的学生。) industrial: 工业的，产业的。如：Italy is becoming an industrial nation.(意大利逐步成为工业国。)
policeman: 指某个具体的警察 police: 警察的总称,后接复数谓语动词, The police are questioning everyone in the house.