五、阅读理解
When autumn arrives in the United States and Canada, you can see one of nature's greatest scenes—the yearly migration of the monarch butterflies(帝王蝶).
No other butterfly in the world migrates like the orange and black monarchs of North America. They cannot live for long periods in cold weather. For this reason, each autumn around October, the butterflies from Canada travel up to 3,000 kilometres south to spend the winter in warmer locations. Some even fly to the mountains of Mexico. There are so many of them that they almost block out the sky. You can even hear their wings beating.
It usually takes the butterflies two months to reach the south of Mexico. After spending five months there, they head back north in the spring. They lay eggs along the way and die. Three generations of butterflies will live and die during the spring journey. The fourth and final generation of the year is born in early autumn and will reach the north. But the butterflies hardly get to rest before starting the long journey south again to Mexico.
The most amazing thing about these butterflies is that they return to the very same trees in Mexico that their great-great-grandparents used the winter before.
However, the population of this colourful butterfly has dropped in recent years. In 2015, the US Fish and Wildlife Service said that nearly a billion monarchs had disappeared from the overwintering sites(越冬地点) since 1990, reported the Washington Post. One of the main reasons, experts say, is that farmers have used herbicides(除草剂) on plants that the monarchs' larvae(幼虫) live and feed on.
()1. How often do the monarch butterflies migrate?
A. Twice a year.
B. Once a year.
C. Once a month.
()2. Why do monarch butterflies fly to the south every autumn?
A. To find suitable places to lay eggs.
B. To avoid the strong winds in the north.
C. To look for a warmer place to live.
()3. What can we know according to the passage?
A. The butterflies spend two months staying in the south of Mexico.
B. The butterflies will get to rest before starting the long journey south again to Mexico.
C. The butterflies that fly back to the north are not the same ones that flew to the south.
()4. What is the main idea of the passage?
A. The harm of farm herbicides to monarch butterflies.
B. Special winter homes of monarch butterflies in Mexico.
C. The migration of monarch butterflies and the dangers they face.

1. A 2. C 3. C 4. C

【分析】
做本题需先通读全文把握核心内容，再针对每道题的问题回到原文定位对应信息，逐一分析选项排除错误答案：1. 第1题需找帝王蝶迁徙频率的描述；2. 第2题需定位南迁原因的相关语句；3. 第3题要核对选项与原文细节是否一致；4. 第4题需综合全文概括主旨，排除片面选项。
【解析】
1. 第1题：根据原文第一段“the yearly migration of the monarch butterflies”及第三段内容，帝王蝶秋季南迁越冬、春季北返，秋季再次南迁，一年迁徙两次，对应选项A，故选A。
2. 第2题：根据原文第二段“They cannot live for long periods in cold weather. For this reason, each autumn... travel... south to spend the winter in warmer locations”，可知帝王蝶秋季南迁是为了寻找温暖的地方过冬，对应选项C，故选C。
3. 第3题：A选项：原文提到到达墨西哥南部需两个月，在当地停留五个月，并非停留两个月，错误；B选项：原文明确说明“But the butterflies hardly get to rest before starting the long journey south again”，并非能休息，错误；C选项：原文提到春季北返的是三代蝴蝶，秋季南迁的是第四代，往返的不是同一批，正确，故选C。
4. 第4题：文章前半部分介绍帝王蝶的迁徙情况，后半部分讲述其数量下降面临的危险；选项A仅涉及除草剂危害，选项B仅提及越冬地点，均片面；选项C涵盖两方面核心内容，故选C。
【答案】
1. A 2. C 3. C 4. C
【知识点】
英语阅读理解、细节理解、主旨归纳
【点评】
本题围绕帝王蝶的迁徙及生存现状展开，重点考查学生定位原文细节、理解语篇主旨的能力，整体难度适中，需学生仔细比对选项与原文信息。
【难度系数】
0.6