登录
C
体裁: 说明文
主题: 科普知识
难度: ★★★★★
建议用时: 9 min
正确率: /4
What are carbohydrates(碳水化合物)?
Carbohydrates are one of the three main things in food, along with fats. Eating them gives you energy. They come in three forms—sugar, starch(淀粉), and fiber—and some foods have all three. Sugars are simple carbohydrates because the body breaks them down quickly. Starch and fiber are complex carbohydrates because they take longer to process. Starch has to be broken down into sugar before it can become energy. Fiber is not broken down but helps the body deal with other things.
①Starchy foods, such as bread, noodles, potatoes, and rice—are popular all over the world. Starch is a type of carbohydrate, which is an important part of the human diet. It provides energy for humans. Now, a study has shown that humans' love for these foods can date back to more than 800,000 years ago, to the DNA of ancient humans, which carries information about a person's body and characteristics.
②In the study, researchers studied the genomes(基因组) of 68 ancient humans, including one that lived 45,000 years ago. A genome is a complete set of DNA. The researchers paid attention to a specific gene called AMY1.
③AMY1 produces(生产) one special thing, which helps humans break down starch in foods. Humans are able to produce many copies(副本) of the AMY1 gene, but the number of copies people have is different from person to person.
④The first crops grown by humans, around 12,000 years ago, were all starchy. However, the team found that humans had many copies of AMY1 thousands of years ago, long before they had begun to grow crops. In fact, Neanderthals and Denisovans, both early relatives of modern humans, also had copies of AMY1. This makes researchers think that the gene dates back more than 800,000 years—that's before Neanderthals, Denisovans, and Homo sapiens (today's humans) even grew into separate species.
⑤The research challenges the idea that before early humans started farming, they ate mainly meat. Kwondo Kim, one of the study's writers, said that the gene became very useful when humans started farming food. Given that the gene appeared so early in our history, the researchers think it may have other good points, perhaps allowing(允许) humans to get more energy from carbohydrates, as well as helping to break them down.
1. What does the underlined word "complex" mean? ＞＞ 词义猜测题
A. Easy. B. Same. C. Difficult. D. Common.
2. 新趋势·补全文章 The following sentence would best be placed at the end of
The more copies people have, the better their ability to break down carbohydrates will be.
＞＞ 补全文章解题策略见 P31 重点精讲
A. Paragraph ② B. Paragraph ③ C. Paragraph ④ D. Paragraph ⑤
3. What can we learn about AMY1 in the passage?
A. It is useful to turn into energy.
B. It is useful to break down energy.
C. It appeared after humans started farming.
D. It appeared before humans ate mainly meat.
4. The main purpose(目的) of the passage is to
A. show the importance of starchy foods
B. explain why humans love starchy food
C. study what carbohydrates and AMY1 are
D. compare ancient humans with today's humans
体裁: 说明文
主题: 科普知识
难度: ★★★★★
建议用时: 9 min
正确率: /4
What are carbohydrates(碳水化合物)?
Carbohydrates are one of the three main things in food, along with fats. Eating them gives you energy. They come in three forms—sugar, starch(淀粉), and fiber—and some foods have all three. Sugars are simple carbohydrates because the body breaks them down quickly. Starch and fiber are complex carbohydrates because they take longer to process. Starch has to be broken down into sugar before it can become energy. Fiber is not broken down but helps the body deal with other things.
①Starchy foods, such as bread, noodles, potatoes, and rice—are popular all over the world. Starch is a type of carbohydrate, which is an important part of the human diet. It provides energy for humans. Now, a study has shown that humans' love for these foods can date back to more than 800,000 years ago, to the DNA of ancient humans, which carries information about a person's body and characteristics.
②In the study, researchers studied the genomes(基因组) of 68 ancient humans, including one that lived 45,000 years ago. A genome is a complete set of DNA. The researchers paid attention to a specific gene called AMY1.
③AMY1 produces(生产) one special thing, which helps humans break down starch in foods. Humans are able to produce many copies(副本) of the AMY1 gene, but the number of copies people have is different from person to person.
④The first crops grown by humans, around 12,000 years ago, were all starchy. However, the team found that humans had many copies of AMY1 thousands of years ago, long before they had begun to grow crops. In fact, Neanderthals and Denisovans, both early relatives of modern humans, also had copies of AMY1. This makes researchers think that the gene dates back more than 800,000 years—that's before Neanderthals, Denisovans, and Homo sapiens (today's humans) even grew into separate species.
⑤The research challenges the idea that before early humans started farming, they ate mainly meat. Kwondo Kim, one of the study's writers, said that the gene became very useful when humans started farming food. Given that the gene appeared so early in our history, the researchers think it may have other good points, perhaps allowing(允许) humans to get more energy from carbohydrates, as well as helping to break them down.
1. What does the underlined word "complex" mean? ＞＞ 词义猜测题
A. Easy. B. Same. C. Difficult. D. Common.
2. 新趋势·补全文章 The following sentence would best be placed at the end of
B
.The more copies people have, the better their ability to break down carbohydrates will be.
＞＞ 补全文章解题策略见 P31 重点精讲
A. Paragraph ② B. Paragraph ③ C. Paragraph ④ D. Paragraph ⑤
3. What can we learn about AMY1 in the passage?
A. It is useful to turn into energy.
B. It is useful to break down energy.
C. It appeared after humans started farming.
D. It appeared before humans ate mainly meat.
4. The main purpose(目的) of the passage is to
B
.A. show the importance of starchy foods
B. explain why humans love starchy food
C. study what carbohydrates and AMY1 are
D. compare ancient humans with today's humans
答案
C
【语篇解读】本文是一篇说明文。文章主要介绍了碳水化合物，人类对淀粉类食物的偏好以及 AMY1 基因在人类分解淀粉中的作用。
1. C 词义猜测题。根据“Sugars are simple carbohydrates because the body breaks them down quickly. Starch and fiber are complex carbohydrates because they take longer to process.”可知淀粉和纤维相比糖需要更长的时间来处理，因此它们是复杂的碳水化合物，画线词表示“复杂的；困难的”。故选 C。
＞＞ 逻辑关系、上下文语境
2. B 补全文章题。第三段介绍了 AMY1 基因的功能以及人类携带基因副本数量的个体差异，题干中给出的句子进一步解释了这一差异带来的影响——AMY1 基因副本数量越多，分解碳水化合物的能力越强。故选 B。
干扰项分析
第二段介绍了研究基因组并关注 AMY1 基因，第四段介绍了基因的历史起源，第五段介绍基因的作用，均未涉及基因副本数量与分解能力的关系。
3. A 细节理解题。根据第三段“AMY1 produces one special thing, which helps humans break down starch in foods.”和最后一段“the researchers think it may have other good points, perhaps allowing humans to get more energy from carbohydrates, as well as helping to break them down”可知 AMY1 基因有助于人类分解食物中的淀粉，并且可能允许人类从碳水化合物中获取更多的能量。故选 A。
4. B 推理判断题。结合文章内容，尤其是第一段“Now, a study has shown that humans' love for these foods can date back to more than 800,000 years ago, to the DNA of ancient humans”可知，本文主要围绕人类对淀粉类食物的偏好以及 AMY1 基因在其中的作用展开，解释了人类喜欢淀粉类食物的原因。故选 B。
【语篇解读】本文是一篇说明文。文章主要介绍了碳水化合物，人类对淀粉类食物的偏好以及 AMY1 基因在人类分解淀粉中的作用。
1. C 词义猜测题。根据“Sugars are simple carbohydrates because the body breaks them down quickly. Starch and fiber are complex carbohydrates because they take longer to process.”可知淀粉和纤维相比糖需要更长的时间来处理，因此它们是复杂的碳水化合物，画线词表示“复杂的；困难的”。故选 C。
＞＞ 逻辑关系、上下文语境
2. B 补全文章题。第三段介绍了 AMY1 基因的功能以及人类携带基因副本数量的个体差异，题干中给出的句子进一步解释了这一差异带来的影响——AMY1 基因副本数量越多，分解碳水化合物的能力越强。故选 B。
干扰项分析
第二段介绍了研究基因组并关注 AMY1 基因，第四段介绍了基因的历史起源，第五段介绍基因的作用，均未涉及基因副本数量与分解能力的关系。
3. A 细节理解题。根据第三段“AMY1 produces one special thing, which helps humans break down starch in foods.”和最后一段“the researchers think it may have other good points, perhaps allowing humans to get more energy from carbohydrates, as well as helping to break them down”可知 AMY1 基因有助于人类分解食物中的淀粉，并且可能允许人类从碳水化合物中获取更多的能量。故选 A。
4. B 推理判断题。结合文章内容，尤其是第一段“Now, a study has shown that humans' love for these foods can date back to more than 800,000 years ago, to the DNA of ancient humans”可知，本文主要围绕人类对淀粉类食物的偏好以及 AMY1 基因在其中的作用展开，解释了人类喜欢淀粉类食物的原因。故选 B。
解析
【分析】
本题为科普类说明文阅读，包含词义猜测题、补全文章题、细节理解题、主旨大意题四种题型。解题思路如下：1. 词义猜测题：定位画线词所在句的上下文，通过对比逻辑推断词义；2. 补全文章题：分析待填句子核心内容，匹配各段落主题确保衔接自然；3. 细节理解题：根据题干关键词定位原文对应段落，比对选项与原文表述的一致性；4. 主旨大意题：梳理文章核心内容，提炼作者写作目的，排除片面选项。
【解析】
1. 词义猜测题：根据原文第一段“Sugars are simple carbohydrates because the body breaks them down quickly. Starch and fiber are complex carbohydrates because they take longer to process.”可知，simple（简单的）与complex形成对比，complex的原因是“需要更长时间处理”，故意为“复杂的、困难的”，选C。
2. 补全文章题：待填句子核心为“AMY1基因副本数量越多，分解碳水化合物能力越强”，对应第三段内容——第三段介绍AMY1的功能及人类携带该基因副本数量的个体差异，与待填句衔接紧密，故选B。
3. 细节理解题：定位第三段“AMY1 produces one special thing, which helps humans break down starch in foods”和最后一段“perhaps allowing humans to get more energy from carbohydrates”，可知AMY1有助于分解淀粉并帮助获取能量，A选项符合；B选项“break down energy”表述错误；C选项与原文“long before they had begun to grow crops”矛盾；D选项无依据，故选A。
4. 主旨大意题：文章围绕“人类对淀粉类食物的偏好”展开，通过AMY1基因的研究解释了人类喜欢这类食物的原因，B选项符合；A选项片面强调淀粉类食物重要性，C选项未突出核心，D选项偏离主题，故选B。
【答案】
1. C 2. B 3. A 4. B
【知识点】
说明文阅读、词义猜测、细节理解
【点评】
本文是围绕碳水化合物与AMY1基因展开的科普说明文，题型全面，需学生准确把握上下文逻辑和原文细节，理清段落关联，整体需细致分析。
【难度系数】
0.5
本题为科普类说明文阅读，包含词义猜测题、补全文章题、细节理解题、主旨大意题四种题型。解题思路如下：1. 词义猜测题：定位画线词所在句的上下文，通过对比逻辑推断词义；2. 补全文章题：分析待填句子核心内容，匹配各段落主题确保衔接自然；3. 细节理解题：根据题干关键词定位原文对应段落，比对选项与原文表述的一致性；4. 主旨大意题：梳理文章核心内容，提炼作者写作目的，排除片面选项。
【解析】
1. 词义猜测题：根据原文第一段“Sugars are simple carbohydrates because the body breaks them down quickly. Starch and fiber are complex carbohydrates because they take longer to process.”可知，simple（简单的）与complex形成对比，complex的原因是“需要更长时间处理”，故意为“复杂的、困难的”，选C。
2. 补全文章题：待填句子核心为“AMY1基因副本数量越多，分解碳水化合物能力越强”，对应第三段内容——第三段介绍AMY1的功能及人类携带该基因副本数量的个体差异，与待填句衔接紧密，故选B。
3. 细节理解题：定位第三段“AMY1 produces one special thing, which helps humans break down starch in foods”和最后一段“perhaps allowing humans to get more energy from carbohydrates”，可知AMY1有助于分解淀粉并帮助获取能量，A选项符合；B选项“break down energy”表述错误；C选项与原文“long before they had begun to grow crops”矛盾；D选项无依据，故选A。
4. 主旨大意题：文章围绕“人类对淀粉类食物的偏好”展开，通过AMY1基因的研究解释了人类喜欢这类食物的原因，B选项符合；A选项片面强调淀粉类食物重要性，C选项未突出核心，D选项偏离主题，故选B。
【答案】
1. C 2. B 3. A 4. B
【知识点】
说明文阅读、词义猜测、细节理解
【点评】
本文是围绕碳水化合物与AMY1基因展开的科普说明文，题型全面，需学生准确把握上下文逻辑和原文细节，理清段落关联，整体需细致分析。
【难度系数】
0.5
