27. telegram, telegraph

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

26. chick, chicken

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

25. man, a man

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

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

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.

22. damage, damages

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

21. cook, cooker

　cook厨师，cooker厨具 He is a good cook.

20. country, nation, state, land

　country侧重指版图，疆域，nation指人民，国民，民族，state侧重指政府，政体，land国土，国家 The whole nation was sad at the news.

19. couple, pair

　couple主要指人或动物，pair多指由两部分组成的东西 a pair of trousers

18. work, job

　二者均指工作。work不可数，job可数 a good job