1 These are boys. Those ships are Russian those ships are Russian

2 Those women are my sisters.

3 Her hair is always greedy.

(Здесь ничего не меняем,т.к.волосы hair в английском это единственное число)

4 They are cats.

5 The cat caught mice yesterday.

6 There were ladies,gentlemen,boys and girls in the room.

7 In the farm-yard we saw oxen, sheep,cows and geese.

8 Are these workers Englishmen or Germans?

They are Frenchmen.

9 These strawberries are stilll green .

10 Can you see birds in those trees?

11 The stories are very interesting.

12Put these knives on those tables.

13 The children's feet are sore.

14 What are the children's names?

15 These aren't mice

16 These men are engineers.

17 These children are my sons.

18 Those ships are Russian.

19 I need your advice.

(Advice-совет,не имеет множественного числа)

20 These are babies.