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环状沉淀试验反应时间为
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Passage ThreeQuestions 33 to 35 are based on the passage you have just heard.
Questions 19 to 21 are based on the conversation you have just heard.
细菌RNA聚合酶的6亚基是
A Small Event One afternoon in January 1989, Suzan Sharp, 43, and her 8-year-old son, David ,were walking hard across an icy parking lot, when Suzan’’s cane (手杖)slid on the ice . She 【51】 face fist into the mud . David 【52】 to her side . "Are you all right, Mom" 【53】 , Suzan put herself up. "I’’m okay, honey." she said. It had been nearly two years since Suzan had trouble walking. She was falling more 【54】 now. Every inch of ice was a 【55】 danger for her. " I could do something," the boy thought. David, too, was having 【56】 of his own. The boy had a speech defect. At school he 【57】 asked questions or read aloud. One day Davids teacher announced a 【58】 assignment. "Each of you is going to come up with an invention, "she said. This was for "INVENT AMERICA!", a national competition to encourage creativity in 【59】 . An idea hit David one evening. 【60】 only his mothers cane didn’t slip on ice ,he thought. "That’’s it!" David realized. "What if I fixed your cane to a nail stretched out of the bottom" he asked his mother. His mother told him," 【61】 it would scratch floors. " "It looks like a ball-point pen. You take your hand 【62】 the button and the nail returns back up." Hours later the cane was finished. David and his father, Jeff, 【63】 as Suzan used it to walk 50 feet across the 【64】 . "It works!" she said . In July 1989, David was declared national winner at the annual" INVENT AMERICA!" ceremony in Washington D.C.. As David began to make 【65】 appearances, he was forced to communicate more clearly. Today, David is nearly free of his cane which is waiting to be widely used. So the boy who once had trouble talking now hopes to start making canes for people who have trouble walking.
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