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阅读理解 A living robot has been created out of frog skin cells. Xenobots, named after the frog species Xenopus laevis that the cells come from, were first described last year. Now the team behind the robots has improved their design and demonstrated new capabilities. To create the xenobots, Michael Levin at Tufts University in Massachusetts and his colleagues obtained tissue from 24-hour-old frog embryos after very small physical operation. Where the previous version relied on the contraction of heart muscle cells to move them forward by pushing off surfaces, these new xenobots swim around faster. They also live between three and seven days longer than their previous generation, which only lasted about seven days, and have the ability to sense their surroundings to some extent, turning red when exposed to blue light. "The fundamental finding here is that when you free skin cells from their normal context, and you give them a chance to build other things than what they normally build," says Levin. "To me, one of the most exciting things here is that they are plastic. This idea that even normal cells, not genetically modified, are in fact capable of building something completely different." Because they are created from cells, the xenobots eventually break apart and are totally biodegradable, says team member Douglas Blackiston, also at Tufts University. He therefore hopes that they can be used for biomedical and environmental applications. Previous attempts at creating living robots, such as a wirelessly controlled cockroach, have involved dealing with live animals, raising ethical concerns. Xenobots differ from these because they are made entirely of living cells. "The approach here is maybe ethically the least problematic because everything starts with cells. They have no neurons, so it's not an animal," says Auke ljspeert at the Swiss Federal Institute of Technology at Lausanne, who wasn't involved in the research. "It's really cells, so I find it maybe the cleanest way." （1） How were the new xenobots created? A . By making use of frog embryos. B . By relying on heart muscle cells. C . By sensing similar surroundings. D . By exposing them to blue light. （2） Which has the similar meaning to the underlined word "plastic" in Paragraph 3? A . Fragile. B . Stable. C . Flexible. D . Active. （3） What can be inferred from Douglas Blackiston's words? A . The xenobots can't break down easily. B . The xenobots need to be further perfected. C . The xenobots can be applied in other fields. D . The xenobots have already been widely used. （4） What can we learn from the last paragraph? A . The new approach starts with some neurons. B . Xenobots have raised least ethical concerns. C . The wireless controlled cockroach is a failure. D . Previous living robots involve few living animals. 答案： A C C B

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