它是牛的总称,那它本身就是复数概念,不是单数,像people ,police ,这一类的词用法一样,你就当复数用。集体名词,以单数形式出现,但实为复数。people,children,police, cattle是复数 有时family也有此用法(OK :a person,a policeman,a herd of cattle , the English,the British,the French,the Chinese,the Japanese,the Swiss )(Error: a people,a police,a cattle )