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Loga261000
2 năm trước
Giúp mình với mình hứa sẽ đánh giá 5 sao chỉ cần làm ngắn gọn. Cacbon có hai đồng vị bền là X và Y. Đồng vị X có 6 proton, 7 notron, chiếm 1,11%. Đồng vị Y có ít hơn X 1 nơtron. a. Viết kí hiệu nguyên tử của X và Y. b. Tính nguyên tử khối trung bình của Cacbon.
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8.It ………………………………. (not / rain) for a long time. 9.……………… you ……………… (see) my dog? It ………………………… (run away) this morning. 10.We …………………………. (meet) at a party a long time ago, but I …………………….. (not / see) her since then. 11.I ………………………… (see) an interesting book in a bookshop yesterday, but I …………………………… (not / buy) it. 12.My friend …………………………… (fall) from the bicycle because he ……………….… (not / ride) one for ages. 13.His father ………………………………… (die) in 1970, but he ………………………….. (never / visit) his father’s grave since that time. 14.They …………………… (go) to America years ago, but none of them …………………... (come) back since then. 15.A: …………….. you ……………….. (speak) to an Englishman? B: Yes, I …………………….. (have) a short conversation with one last night. 16.A: ………………. you ever ………………….. (be) to Tatilya? B: Yes, I ………………………. (go) there two years ago. 17.A: ………………. you ……………….. (see) Jane recently? B: No, I ……………………………. (see) her for a long time.

giúp mình với ạ 1 Tom said to the girl: "When did you have this picture taken?" => Tom asked the girl...................................................................................................................... 2 " We shall go somewhere for a cup of coffee after class.” => Tom said. ...................................................................................................................... 3 She asked me, "Have you ever seen a flying saucer?" => She askedme........................................................... 4 James said: "Do you want me to type this letter for you now?" => James asked me................................................................ 5 Helen said, "I'll have to find a better job. I can't make both ends meet." => Helen said that............................ 6 He said to her " I am waiting for you at this moment." => He told her that ...................................................................................................................... 7 The boy said to his mother: "When shall we have lunch? I'm very hungry." => The boy asked his mother..................................................................................... 8 He said, "I don't understand why she has refused to join us on the trip." => He said.......................................................................................... 9 Mr Brown said to his wife, "I don't feel like going out this evening.” => Mr Brown said that...................................................................................... 10 “It is raining too hard to go out so we can’t go out."

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