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huynhtan010401
2 năm trước
một vật sáng đặt vuông góc với trục chính của một thấu kính hội tụ tiêu cự 40 cm cách thấu kính 60 cm a.vật đặt ở vị trí nào thì cho ảnh cao bằng vật b.muốn có ảnh ảo cao gấp 2 lần vật thì đặt vật ở đâu
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Many people still (1)_______ that natural resources will never be used up. Actually, the world’s energy resources are (2)_______. Nobody knows exactly how (3)_________ fuel is left. However, we also should use them economically and try to find out alternative sources of power. According to Professor Marvin Burnharm of the New England Institude of Technology, we have to start conserving coal, oil and gas before it is too late; and nuclear power is the only alternative. However, many people do not approve of using nuclear (4)________because it’s very dangerous. What would happen if there was a serious nuclear accident? Radioactivity causes cancer and may badly affect the future generations. The most (5)______ thing is that we should use natural resources as economical (6)______ possible. 1. A. believe B. hope C. like D. dislike 2. A. unlimited B. limited C. abundant D. dangerous 3. A. much B. many C. often D. far 4. A. energy B. renewable C. power D. non-renewable 5. A. effect B. affect C.uneffective D. effective 6. A. in B. to C. as D. than

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