16. Mum is always busy with her work in the laboratory.

17. The clerk at that counter said those purses were on sale.

18. Don't believe her! She just makes up the story.

19. Old people like to descant on past memories.

20. You should comply with the school rules.

21. The price of electricity is going up in August.

22. They came to visit us on my birthday.

23. Did you have a good time on Christmas?

24. The children are very excited for their summer vacation.

25. We were very disappointed of the organization of the festival.

26. John missed a lot of lessons. He was ill from January to March.

27. Helen had said goodbye to everybody in the class before she left from the hometown.

28. My cat is very fond of fish.

29. I waited for 10 oclock and then went home.

30. I can't remember exactly when the accident happened. I think it was between nine and half past nine.