题型：语法填空（语篇） 题类：模拟题 难易度：困难
湖南省师范大学附属中学2020届高三上学期英语考前演练试卷（五）
Many people living in cities see riding a bicycle as good exercise. But, a recent medical research warned that cyclists should think twice before cycling in the streets: it actually does more harm than good their bodies.
Is cycling in cities really bad for your health? Probably yes. The main danger comes from the air around you. Breathing in air pollution from taxis and buses can damage blood vessels(血管).Scientists say the damage could outweigh the health benefits of cycling.
David Newby, a British researcher at Edinburgh University broke the news. In his tests, 15 healthy men cycled on exercise bikes in a room with levels of air pollution similar to those found on a crowded city street. After an hour of cycling, the scientists found their blood vessels became less flexible and produced less of a protein(蛋白质) the heart needs. The damage leads to the early stages of heart disease. What's worse, the faster a cyclist pedals (蹬车), more air they breathe in. So those who believe they are improving their fitness the most are storing up the biggest trouble for .
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