训练3 体裁：说明文 主题：科普知识 难度：★★★★★ 建议用时：8 min 正确率：/4
It’s that time of year when the sun shines warmly, trees get new leaves, and flowers come out. However, for many people, the beauty of spring also brings sneezing, sore skin, and a running nose. Well, spring is the worst allergy(过敏) season.
This is, to a large degree, due to pollen. When winter ends, plants wake up and start shooting pollen into the air. They can produce billions of these tiny pieces every spring. The pieces get swept up by the wind and land everywhere. It’s like a big pollen party in the air!
The problem isn’t with pollen itself. This dust-like thing is produced by plants to reproduce and isn’t meant to harm(伤害) us. But why do some people have bad reactions to it? It’s all because of their immune(免疫) system. The immune system is like a group of soldiers, always ready to fight against harmful things.
Sometimes, the immune system makes a mistake. It thinks pollen is harmful. When this happens, it sends out chemicals(化学物质) that cause allergies, like coughing and sneezing. Why do these allergies get worse? First, pollen only comes in certain seasons, so the immune system can hardly get used to it. Second, the pollen pieces are so small that they easily get into our bodies, making the allergies worse.
Scientists have studied this for a long time. They know genes(基因) play a part. If parents have allergies, their children are more likely to have them. But exactly how do genes lead to allergies? There’s no clear answer. Environmental factors also matter. Many scientists believe that growing up in a completely clean environment affects the immune system. But how does this environment affect the start of an allergy? No one can fully explain it.
Most people with seasonal allergies develop them after reaching adulthood. These allergies can change unexpectedly. In some cases, after years of having allergies, they suddenly disappear one spring. But scientists still have no idea how or why this happens.
1. Why does the writer compare the immune system to soldiers in Paragraph 3?
A. To show why pollen is harmful to the human body.
B. To tell us how pollen brings bad effects to our bodies.
C. To introduce why the immune system makes mistakes.
D. To help readers understand how the immune system works.
2. What makes allergies worse?
A. The immune system knows pollen well.
B. Chemicals cause coughing and sneezing.
C. Pollen appears in different pieces with the seasons.
D. Pollen comes in certain seasons and has tiny pieces.
3. 新趋势·补全文章 Which of the following can be put in the “”?
➤➤补全文章题解题策略见 P31 重点精讲
A. What causes allergies is only genes.
B. How allergies develop is still unknown.
C. What scientists know about allergies matters a lot.
D. How the environment affects allergies is fully understood.
4. What is the best title for this passage?
A. The Role of Pollen in Allergies
B. The Secrets of Spring Allergies
C. The Work of the Immune System
D. The Seasonal Problem of Allergies

1. D 推理判断题。根据第三段“The immune system is like a group of soldiers, always ready to fight against harmful things.”可知将免疫系统比作士兵，形象说明了免疫系统的防御机制。故选 D。
2. D 细节理解题。根据第四段“Why do these allergies get worse? First, pollen only comes in certain seasons ... Second, the pollen pieces are so small that they easily get into our bodies”可知过敏加重的原因是花粉季节性出现导致免疫系统难以适应和微小的花粉颗粒易侵入人体。故选 D。
3. B 补全文章题。根据下文“They know genes play a part ... But exactly how do genes lead to allergies? There's no clear answer. Environmental factors also matter ... But how does this environment affect the start of an allergy? No one can fully explain it.”可知本段介绍了基因如何导致过敏尚不明确，环境如何影响过敏未被完全解释，强调过敏成因的未知性；B项“过敏如何发展尚不清楚”概括了本段的主要内容。故选 B。
4. B 标题归纳题。结合文章内容可知，本文主要介绍了春季过敏的原因，包括花粉的作用、免疫系统的反应以及基因和环境因素的影响，但科学界对其成因尚未完全破解。故选 B。

【分析】这是一篇科普类说明文，围绕春季过敏展开，设置4道阅读理解题，分别考查推理判断、细节理解、补全文章、标题归纳。解题思路为：先通读全文把握主旨，再针对每道题定位原文对应段落，提取关键信息，结合选项排除错误内容，选出正确答案。
【解析】1. 推理判断题：根据第三段“The immune system is like a group of soldiers, always ready to fight against harmful things.”可知，将免疫系统比作士兵，是为了帮助读者理解免疫系统对抗有害物质的工作机制，对应选项D。A选项与原文“花粉本身无害”矛盾；B选项并非比喻的目的；C选项与比喻无关，故选D。2. 细节理解题：根据第四段“Why do these allergies get worse? First, pollen only comes in certain seasons... Second, the pollen pieces are so small that they easily get into our bodies”可知，过敏加重的原因是花粉季节性出现导致免疫系统难以适应，且花粉颗粒微小易侵入人体，对应选项D。A选项与原文逻辑相反；B选项是过敏表现而非加重原因；C选项原文未提及，故选D。3. 补全文章题：第五段下文提到基因如何导致过敏无明确答案，环境影响过敏也未完全解释，强调过敏成因的未知性，B项“过敏如何发展尚不清楚”概括本段内容，对应选项B。A选项与原文“基因和环境都起作用”矛盾；C选项与下文“未知”不符；D选项与原文“未完全解释”矛盾，故选B。4. 标题归纳题：文章围绕春季过敏展开，介绍了花粉作用、免疫系统反应、基因和环境因素的影响，且科学界对其成因尚未完全破解，B项“春季过敏的秘密”最能概括主旨，对应选项B。A、C、D均片面，故选B。
【答案】1.D 2.D 3.B 4.B
【知识点】说明文阅读、细节理解题、推理判断题
【点评】本题为科普类说明文阅读理解，题型全面，考查学生英语阅读的综合能力，需学生具备定位原文、分析逻辑及归纳主旨的能力，是典型的英语阅读练习题。
【难度系数】0.5