中小学教育资源及组卷应用平台 book 2 unit 6 starting out and understanding ideas 课时同步练习 一、单句语法填空 1．It goes that monk named Li Tian created fireworks around 1400 years ago by packing gunpowder into bamboo tubes (scare) off evil spirits. 2．As the impact of human activities continues, the list of species in danger of (extinct) becomes longer. 3． (fortunate), everything worked out all right in the end. 4．The (extinct) of certain species is a major concern for environmentalists. 5．Due his efforts, he was admitted into a key university. 6．When it all gets too much, your parents are often the first (target) of your anger. 7． (fin) the sharks will lead to their death eventually. 8．Recently, the app (target) teenagers as its users. 9．He threw a stone (scare) the dog away. 10．They scared him into (hand) over the money. 二、阅读理解 A “Big Tree,” an old southern live oak, sits in a park just outside Orlando’s business district. It’s been struck by lightning at least three times and has survived many hurricanes — and it grew from a seed around the same time Juan Ponce de León’s ship first landed on Florida’s eastern coast. Over 400 years old, the tree is so impressive that members of a Michigan-based nonprofit flew to Orlando in February to climb the tree and cut branches and leaves. The researchers are now in the midst of the process to grow new roots from the cuttings. The reason: To clone the historic tree, store its DNA and plant potentially thousands of cloned trees across the Southeast. In order to clone an ancient tree, researchers must climb it to find a piece of live tissue. The freshly cut branches and leaves are taken to the group’s lab in Michigan, where, in climate-controlled rooms, researchers work to promote growth from the cuttings. The most common method is by rooted cuttings. In this method, a tip of a tree’s branch is dipped (蘸) into hormones, placed into a foam plug (泡沫塞) and set inside a mist room. Then, the waiting begins. A sign of life can take several months to a year to show, if one comes at all. In another method called tissue culture, researchers take a quarter-inch of branch, dip it into a mixture made up of a dozen hormones and other chemicals, seal(密封) it in a container and wait to see whether it will grow roots. Experts ‘lauded the group for its creative methods and reproduction in large numbers, but they doubt whether the clones will grow as the originals do. Scott Merkle, a professor of forest biology at the University of Georgia, said, “There are so many variables that there’s no certainty that they will be able to survive and perform better than other trees that you plant on the same land”. He added that the age of historic trees makes them difficult to study. “I think it’s a great thing that they’re doing…I just don’t know how realistic it is.” 11．According to the passage, what do the researchers aim to do A．To clone an ancient tree from its original. B．To save thousands ... ...
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