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nguyennhatminh30041976
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Khi lai dòng chó thuần chủng lông đen, chân cao với dòng chó thuần chủng lông trắng, chân thấp thu được F1 gồm toàn chó lông đen, chân cao. Cho chó F1 tự giao phối với nhau thu được F2. Lập luận và viết sơ đồ lai cho phép lai trên.
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AI GIÚP EM VỚI About three thousand years ago, there were no shops. If you needed something you had to make it yourself. For example, if you needed something you wear, you had to kill an animal and get its coat. If you were a good hunter and had a lot of coats, you could exchange them for other things you needed. You could get meat, fruit or an axe. This way of exchanging things is called barter. Later on, people began to use money. They made money from things which would last and not go bad easily. They used stones, shells and animals’ teeth. After men had dicovered metal, they started to use copper, tin, silver and gold. They made these metals into small bar so that they were easy to store and carry about. Before there were banks, people kept their money themslves. Most people hid their money in the ground. They thought it was the safest place to store money. About five hundred years later, people began to make coins.They were easier to carry than metal bars. 1. There were no shops ___________ A. in the 15th century. B. five hundred years ago C. in China and Italy. D. about three thousand years ago. 2. What would you do if you wanted a coat thousands of years ago? A. Go to buy one from a shop. B. Kill an animal for its skin. C. Make friends with hunters D. Make one from cloth 3. The early way of exchanging one thing for another is called __________ A. metal melting B. coin- collecting C. banking D. barter 4. What kind of thing goes bad easily and is not good for making money? A. Metal B. Axe C. Food D. Shells 5. Why did people make coins? A. Coins were beautiful. B. Coins were easy to count C. They liked round coins instead of small bars. D. coins were easier to carry about.

I. Choose the letter A, B, C, D to indicate the correct answer to each of the following questions. Question 1. I _______ at school now. A. am being B. was being C. was D. am Question 2. I _______ to Ho Chi Minh City several times this year. A. have been B. was C. were D. had been Question 3. He _______ here three hours ago. A. is leaving B. left C. has left D. have left Question 4. We _______ Peter since last Monday. A. don’t see B. haven’t seen C. didn’t see D. hadn’t seen Question 5. Tim _______ a book when I came to his house. A. is reading B. read C. was reading D. reading Question 6. My brother _______ badminton. A. usually play B. is usually playing C. usually plays D. have usually played Question 7. I _______ my clothes at 7 o’clock yesterday evening. A. am ironing B. have ironed C. ironed D. was ironing Question 8. My mother _______ English for ten years. A. has learnt B. is learning C. learn D. learns Question 9. _______ you go to the zoo? A. How often are B. How often do C. How often does D. How are Question 10. The sun _______ in the East. A. is rising B. rose C. has risen D. rises Question 11: When I was young, I _______ to be a teacher. A. want B. was wanting C. wanted D. had wanted Question 12. My grandmother _______ 10 years ago. A. had died B. died C. has died D. was dying Question 13. Look at those black clouds. It _______ . A. rains B. is raining C. is going to rain D. rain Question 14. Tomorrow I _______ my parents. A. am going to visit B. will have visited C. have visited D. visit Question 15. She _______ books now. A. is reading B. read C. reads D. was reading II. Put the verbs in the brackets into the correct tense. Question 16. We seldom (eat) __________ breakfast before 7 o’clock. Question 17. What __________ you (do) __________ every morning? Question 18. We (build) __________ this house five years ago. Question 19. It (be) __________ often hot in the summer. Question 20. __________ you (watch) __________ TV yesterday? Question 21. He often (go) __________ fishing with his friends when he was a child. Question 22. We (live) __________ here for 2 years. Question 23. I (not see) __________ him since we (say) __________ goodbye. Question 24. Nam and I (play) __________ soccer at 3 p.m yesterday. Question 25. While I (cook) _________ dinner, my sister (read) _______ books last night. Question 26. He always (forget) __________ his homework. He isn’t careful. Question 27. We (be) __________ close friends since last year. Question 28. Uncle Ho (die) __________ in 1969. Question 29. We (buy) __________ a new car next year. Question 30. Keep silent! The baby (sleep) __________ .

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