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 conquer nature.
26. chick, chicken
二者均可指小鸡，chicken还可以当鸡肉 The chicken is delicious.
27. telegram, telegraph
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.