people　police　cattle 等本身就是复数，不能说 a people，a police，a cattle，但可以说a person，a policeman，a head of cattle.
（2） 否定句：主语+does not / doesn't+动词原形+其他.
例如： Henry doesn't have any brothers.
（3）一般疑问句：Does+主语+动词原形+其他? 肯定回答：Yes, 主语+does. 否定回答：No, 主语+doesn't.
例如： ―Does he work in the hospital?
―Yes, he does. / No, he doesn't.
例如： When does Li Ming do his homework every day?