-Khi điều chế Clo từ NaCl bằng phương pháp điện phân dung dịch thì tại sao thiết bị phải có màng ngăn? - tại sao khi mở bình khí đựng dung dịch HCl đậm đặc trong không khí ẩm lại thấy hiện tượng bốc khói

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I. Choose the word or phrase (A, B, C, or D) that best fits the blank space in each sentence 1. He gets up early in the morning to ___________exercises. A. do B. make C. play D. practice 2. Sometimes I ___________my own washing and ironing. A. do B. did C. am doing D. will do 3. The farmers___________ on the farm now. A. work B. are working C. worked D. will work 4. Don’t forget _________your teeth before going to bed. A. brush B. to brush C. brushing D. not to brush 5. She was sick, but now she feels __________again. A. good B. well C. badly D. best 6. You have to take care of _________when you are away from home. A. you B. your C. yours D. yourself 7. When you have a toothache, you should go to the_________. A. doctor’s B. dentist’s C. chemist’s D. canteen 8. Children are ____________of going to see the dentist. A. enjoyable B. pleased C. afraid D. keen 9. Children should go to bed__________. A. early B. late C. on time D. soon 10. If you eat ____________candy, you will get a toothache. A. much B. many C. lots D. a lot 11. The dentist ___________a cavity in Minh’s tooth. A. did B. made C. filled D. pulled 12. After the dentist filled the cavity in his tooth, it stopped____________ A. hurt B. hurting C. to hurt D. to hurting 13. Don’t worry. The dentist ________ how to fill the cavity in the tooth very well. A. knows B. knew C. is knowing D. will know 14. The sound of the drill was so ____________that I felt scared. A. loud B. loudly C. louder D. loudest 15. Farmers are always busy at___________. A. harvest’s time B. harvesting time C. harvest time D. time harvesting 16. What should you do _____________yourself clean and tidy? A. to take B. to do C. to make D. to give 17. .____________ do you brush your teeth? - Twice a day. A. How B. How often C. How much D. How long 18. Eating too much candy is not good for your_____________. A. tooth B. teeth C. healthy D. healthful 19. I can’t chew because I have a_______________. A. headache B. stomachache C. toothache D. cold 20. I hate the ___________ of the drill at the dentist’s. A. noise B. sound C. voice D. music