21. cook, cooker

cook 廚師，例：He is a good cook.
cooker 廚具。

22. damage, damages

damage 不可數(shù)名詞，損害，損失；
damages 復數(shù)形式，賠償金，例：$900 damages

23. police, policeman

police 警察的總稱，后接復數(shù)謂語動詞，例：The police are questioning everyone in the house.
policeman 指某個具體的警察。

24. problem, question

problem 常和困難連系，前面的動詞常為think about, solve, raise；
question 常和疑問連系，多和ask, answer連用。

25. man, a man

man 人類；
a man 一個男人，例：Man will conquer nature.