21. cook, cooker

　cook厨师，cooker厨具 He is a good cook.

22. damage, damages

　damage不可数名词, 损害，损失; damages复数形式, 赔偿金 $900 damages

23. police, policeman

　police警察的总称，后接复数谓语动词，policeman 指某个具体的警察 The police are questioning everyone in the house.

24. problem, question

　problem常和困难连系，前面的动词常为think about, solve, raise，question常和疑问连系，多和ask, answer连用

25. man, a man

　man人类，a man一个男人 Man will conquer¹ nature.

26. chick, chicken

　二者均可指小鸡，chicken还可以当鸡肉 The chicken is delicious.

27. telegram, telegraph²

　当电报解时，telegram指具体的，telegraph指抽象的 a telegram, by telegraph

28. trip, journey, travel, voyage

　travel是最常用的，trip指短期的旅途，journey指稍长的旅途，voyage指海上航行

a three-day trip

29. sport, game

　sport多指户外的游戏或娱乐活动，如打球，游泳，打猎，赛马等；game指决定胜负的游戏，通常有一套规则 His favorite sport is swimming.

30. price, prize

　price价格，prize奖，奖品，奖金 win the first prize The price is high/low.