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nguyentai23012003
2 năm trước
Để sản xuất Mg từ nước biển, người ta điện phân muối MgCl2 nóng chảy. Trong quá trình sản xuất người ta dựa vào tính chất nào? A. Mg(OH)2 là chất k tan B. Mg(OH)2 tác dụng dễ dàng với HCl C. MgCl2 nóng chảy ở nhiệt độ tương đối thấp D. A,B,C đúng
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X. Read the passage and answer the questions. KEEPING OUR TEETH HEALTHY It‟s very important to have healthy teeth. Good teeth help us chew our food. They also help us look nice. How does a tooth go bad? The decay begins in a little crack in the enamel covering of the tooth. This happens after germs and bit of food have collected there. Then the decay slowly spreads inside to the tooth. Eventually, poison goes into the blood, and we may feel quite ill. How can we keep our teeth healthy? First, we ought to visit the dentist twice a year. He can fill the small holes in our teeth before they destroy the teeth. He can examine our teeth to check that they are growing in the right way. Secondly, we should brush our teeth with a toothbrush and fluoride toothpaste at least twice a day-once after the breakfast and once before we go to bed. We can also use wooden toothpicks to clean between our teeth after a meal. Thirdly, we should eat food that is good for our teeth and our body: milk, cheese, fish, brown bread, potatoes, red rice, raw vegetables, and fresh fruits. Chocolates, sweets, biscuits and cakes are bad, especially when we eat them between meals. They are harmful because they stick to our teeth and cause decay. 1 .Good teeth help us …………………. our food. A. be nice B. have good eyesight C. chew D. be important 2. When food and germs collect in a small crack, our teeth …………………. A. become hard B. send poison into the blood C. begin to decay D. make us feel quite ill 3. A lot of people visit the dentist only when …………………. A. their teeth grow properly B. they have holes in their teeth C. they have toothache C. they have brush their teeth 4. We ought to clean our teeth …………………. A. After breakfast B. before breakfast C. before bedtime D. Both B &C 5. We shouldn‟t eat a lot of …………………. A. red rice B. fresh fruit C. fish D. chocolate

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