When people lo legs after accidents or illness, emergency care and artificia

题文

When people lo legs after accidents or illness, emergency care and artificial limbs（假肢）often allow them to walk again. Newts （蝾螈） in the same situation, on the other hand, can grow limbs back on their own! Scientists have known for a long time that certain animals can re-grow limbs, but they haven’t quite figured out how the creatures do it.Rearchers have now come up with some new ideas. Their work may give people the ability to re-grow lost limbs. The rearchers started with two simple experiments：when you cut a newt’s leg at the ankle, only the foot grows back；when you cut off a leg at the very end, the whole leg grows back. In both cas, the re-growth begins with stem cells. Stem cells can develop into nearly any type of cell in the body.How do a newt’s stem cells know when to grow only a foot and when to re-grow a whole leg?This question relates to another mystery. In newt’s, a cut-off leg will grow back only if the nerve bundle（神经束）in it also grows back , but if something prevents the nerve bundle from growing, the stem cells at the wound won’t re-grow a new leg.In its study, a British team focud on a protein called n-AG. When the team prevented nerves in a limb from growing, but added the n-AG protein to stem cells in the limb, the limb still re-grew. That protein ems to guide limb re-growth. People have proteins that are similar to n-AG. Further rearch into the materials may someday help human limbs recover by themlves.40. In the experiments, the rearchers cut off a newt’s foot or leg to find out _____.A. what stem cells wereB. whether they would grow backC. how long it would take to re-grow    D. how they would re-grow41. A newt will re-grow its leg if _____.A. its ankle was cut off but the nerve bundle was goodB. its leg was cut off and the nerve bundle stopped growingC. its leg was cut off and the nerve bundle could grow backD. its ankle and the nerve bundle were cut off42. What do the underlined words “the materials” refer to?A. Nerve bundles and proteins. B. Proteins similar to n-AG.C. Stem cells and proteins.  D. Stem cells and nerve bundles.43. The first ntence of the passage _____.A. acts as a lead–in  B. shows where rearchers got their new ideasC. states the author’s opinion   D. describes the result of rearchers’ studies 题型：未知难度：其他题型

答案

40-43 DCBA

解析

略

考点

据考高分专家说，试题“When people lo leg.....”主要考查你对 [健康环保类阅读 ]考点的理解。 健康环保类阅读

健康环保累阅读概念：

健康环保类文章常是介绍科学知识、生活常识和环境保护方面的短文。体裁有记叙文、 说明文、议论文和各种应用文。

健康环保类文章阅读技巧：

   健康环保类文章常是介绍科学知识、生活常识和环境保护方面的短文。阅读此类短文要以现象或事物为中心进行思考，理解现象产生的原因、条件和客观规律等。同时要抓住事物的特征、用途和相互关系等。科普环保类文章一般为说明文，从结构上看大致可分为三个部分：   第一部分一般是文章的首段，主要用来提出文章的主题，即文章想要阐述、说明的主要内容；   第二部分是文章的主体，可由若干个段落组成，对文章的主题进行展开说明；   第三部分是结尾段，对文章的主题进行归纳总结。这类文章多用一般现在时，而且一般多使用客观性词语表述。有时为了强调客观性，也常使用被动语态。   从近几年的考试题来看，科普环保类的文章越来越与人们的实际生活相接近。由于此类文章缺乏故事情节，很多同学对此类文章感到费解。但一般的科普类文章都是就事论事，需要逻辑推理和想象的时候较少，因此此类阅读题也没有同学们想象中的那么难，只要多加训练，就能较好地答题。【阅读策略】 1、概要(Summarizing)：  阅完材料后，将所阅材料浓缩，摘要，做出所阅材料的书面或口头梗概。 2、组织(Organization)：  阅读后根据阅读内容，识别观点、人物、事件之间的关系以及文章的结构关系。如：时间关系、比较或对比关系、相关关系及因果关系等。