IV. Fill in the blank with although, and, because, but, or, since, so, unless, until, when. 15. She has not called __________ she left last week. 16. I saw him leaving an hour __________ two ago. 17. This is an expensive __________ very useful book. 18. We will go swimming next Sunday __________ it's raining. 19. I heard a noise __________ I turned the light on. V. Each of the following sentences has one mistake. Identify and correct the mistakes( Mỗi câu sau đây mắc một lỗi. Xác định và sửa chữa những sai lầm) 20. The children have put away their toys but they didn’t make their beds yet. 21. Would you mind waiting little minutes? 22. When we were on holiday, we spent too a lot of money. 23. Some flowers bought for his mother on her birthday yesterday. 24. A new high school builds in our town next year.