Passage two
It starts with a cough or a wheeze. Soon your chest feels tight，your breathing speeds up and gets shallower，making you feel short of breath. These are common symptoms of an asthma attack. Around the world, more than 300 million people suffer from asthma and around 250,000 people die from it each year. Asthma affects the respiratory system，particularly the smaller airways，such as the bronchi or bronchioles.Although we have come a long way in improving how we treat and diagnose asthma，we still do not know its exact causes. We currently believe that a combination of genetic and environmental factors plays a role potentially acting during early childhood. Recent research has even linked poverty to asthma incidence. This may be due to reasons ranging from exposure to additional pollutants and environmental irritants to difficulties in obtaining medical care or treatment.
发病初期会咳嗽或喘息。很快便会胸闷，呼吸急促而浅，使人感觉气短。这些都是哮喘发作的典型症状。全球有超过 3 亿哮喘患者，每年约 25 万人死于哮喘。哮喘会损害呼吸系统，尤其是细小气道，比如支气管与细支气管。
尽管如今我们在哮喘的诊断与治疗手段上已有长足进步，但该病的确切病因仍未探明。目前医学界认为，遗传与环境两类因素共同诱发哮喘，且相关影响多在幼儿时期就开始显现。近期研究甚至发现贫困和哮喘发病率存在关联。背后成因多样：长期接触各类污染物、环境刺激物，或是难以获得医疗诊治，都可能导致这一现象。
Questions number 19 to 21 are based on the passage you've just heard.
19.What does the beginning of the passage talk about？
文章开篇介绍了什么内容？
20.How many people die from asthma each year？
每年有多少人死于哮喘？
21.what can we learn about asthma from the passage？
我们能从文中了解到关于哮喘的哪些信息？
我查了一下，
这篇短文的题源可能来自于梅奥官网的哮喘疾病，
下面我把梅奥关于哮喘的内容发给大家，
下周我将分解这篇内容，
我们把这个五页的内容学习掉。
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文章的最后，
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听力早一点开始复习，
可以参加我们的两个课程：
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