17 Một đoạn phân tử ADN có tổng số 150 chu kì xoắn và adenin chiếm 30% tổng số nucleotit. Tổng số liên kết hidro của đoạn ADN này là A. 3000 B. 3100 C. 3600 D. 3900 18. Số liên kết hydro giữa các cặp G và X bằng 1,5 số liên kết hydro giữa các cặp A và T. Tỉ lệ % tương ứng nucleotit của gen lần lượt là A. A = T = G = X = 25% B. A = T = 20% ; G = X = 30% C. A = T = 30% ; G = X = 20% D. A = T = 15% ; G = X = 35% 19. *Một gen có 900 cặp nucleotit và có tỉ lệ các loại nucleotit bằng nhau. Số liên kết hydro của gen là A. 1798 B. 2250 C. 1125 D. 3060 Xin cách giải ạ ♥️

a, cho a,b,c là các số dương thỏa mãn a^3/b+b^3/c+c^3/a=ab+ac+bc Tình giá trị của biểu thức M=(a+b+c).(1/2014a+1/2014b+1/2014c)

Cho` triangle ABC`. Trên cạnh `BC` lấy điểm `I` sao cho `BI=1/3 BC`. Chứng minh: `vec{BI}=-1/2 (vec{AI}-vec{CA})`

tính chính xác 20072008 × 20202021

Thực hiện phép tính sau: 1+2-3-4+5+6-7-8+9+...+2018-2019-2020+2021

tìm giá trị biểu thức giải kĩ giúp em!

Exercise 2: Put the verbs in bracket into the past simple or the present perfect 1. I ______ (not/play) tennis since I was at school but I _____ (be) very good at it back then. 2. A: ______ you ________ (choose) a dress for the party yet? B: Yes, I ______ (buy) one yesterday. 3. I think our teacher ______ (forget) about the test! He ___________ (not/ say) anything about it in the last season! 4. A: ____________ (you/ sell) your house yet? B: Yes, some people _______ (see) it last month and ________ (buy) it. 5. They __________ (lose) their cat. It ___________ (run) away last week. 6. __________ Helen ever __________ (try) sushi? 7. __________ you __________ (go) to the wedding last night? 8. I __________ never __________ (be) to Paris 9. This year I __________ (travel) to Athens 3 times so far. 10. Paul and Judith __________ (be) married since 1998. 11. __________ you __________ (finish) your homework yet? 12. Last night aunt Betty __________ (come) by. She __________ (tell) us that this summer they are going to Hawaii. 13. I __________ (visit) many different countries so far. Last summer I __________ (go) to Italy and 3 years ago I __________ (be) in Spain. I __________ (not/ visit) Germany yet. 14. When __________ you __________ (come) to Greece? 15. I __________ (come) in 2007. 16. __________ you __________ (watch) the film E.T. yesterday? 17. They __________ already __________ (leave) the train station 18. How long __________ you __________ (know) Jonathan? 19. I __________ (meet) him in 2009, so I __________ (know) him for 3 years 20. What __________ (happen) to Lucy last night? 21. __________ you __________ (read) “Harry Potter” when you were on holidays?

Ex1 Choose the word whose underlined part is pronounced differently. 1. A. suffered B. entertained C. polluted D. unemployed 2. A. sights B. problems C. souvenirs D. exhibition 3. A. around B.sound C. about D. country 4. A. question B. attraction C. education D. tradition 5. A. advice B. decision C. delighted D. helpline 6.A. embarrass B. missing C. classmate D. pressure 7. A. adolescence B. emergency C. helpline D. tense 8.A. delighted B. depressed C. embarrassed D. stressed

30. Young people want to go to the city to study, they____________better education. A. expectation B. expectable C. expectably D. expect 31. At first, Na felt hard to live in Ha Noi, then she was given______________,she feels better now. A, a head B. a love C. a hand D. a look 32.I’ll take you to the market later, if you like? - “________________” A. Wonderful B. You’re welcome C. Yes, I like it D. Not at all 34. Shall we rebuild some buildings in this city next year?- “________________” A, No, we can’t B.You’are welcome C. All right D. You needn’t do that 35.She told her mother that _____ a very high score in her test. A. she had got B. she had get C. she has getD. she has got

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