When autumn arrives in the United States and Canada, you can see one of nature’s greatest scenes—the yearly migration(迁徙) of the monarch butterflies(帝王蝶).
No other butterfly in the world migrates like the orange and black monarch of North America. They can not live for long periods in cold weather. So each autumn around October, the butterflies travel up to 3,000 kilometers south to spend winter. Some even fly to the mountains of Mexico.
It usually takes the butterflies two months to reach Mexico. When it is warm, they start to back north in the spring. But not one butterfly finishes the whole trip. They lay eggs along the way and die. It might take the monarchs as many as four to five generations(代) to complete the journey all the way back up to Canada, says Sarina Jepsen, who directs the endangered species program for the Xerces Society.
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 number of these colorful butterflies has dropped in recent years. The US Fish and wildlife Sen ice said that nearly a billion monarchs have disappeared from overwintering sites(越冬地点) since 1990, theWashington Postreported, one of the main reasons, experts say, is that farmers have used herbicides(除草剂) on the milkweed(马利筋) plants that these butterflies feed on.
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11.What color are the monarch butterflies?______
A.Orange and black.
B.Pink and black.
C.Orange and white.
12.How long does it take the monarch butterflies to reach Mexico?______
A.One month.
B.Two months.
C.Four to five generations.
13.What is the most amazing thing about the monarch butterflies?______
A.They migrate to visit their friends.
B.They are protected by their family members.
C.They can return to the same trees that their ancestors lived in.
14.From the passage, we know that the number of the monarchs has dropped mainly because of ______.
A.less food
B.bad weather
C.air pollution
15.What might the writer talk about next after the passage?______
A.How to plant more trees.
B.How to research these butterflies.
C.What we can do to protect these butterflies.
答案解析：
11. A. Orange and black.
解析：根据文章第二段，"No other butterfly in the world migrates like the orange and black monarch of North America." 可以得知，帝王蝶的颜色是橙色和黑色。
12. B. Two months.
解析：文章第三段提到，"It usually takes the butterflies two months to reach Mexico." 表明帝王蝶通常需要两个月的时间才能到达墨西哥。
13. C. They can return to the same trees that their ancestors lived in.
解析：文章第四段提到，"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." 说明帝王蝶最令人惊讶的是它们能够返回到它们的曾祖父母前一年冬天居住的同一棵树上。
14. A. less food
解析：文章最后一段提到，"one of the main reasons, experts say, is that farmers have used herbicides on the milkweed plants that these butterflies feed on." 说明帝王蝶数量减少的主要原因是农民使用了除草剂，杀死了帝王蝶赖以生存的马利筋植物，即食物减少。
15. C. What we can do to protect these butterflies.
解析：文章最后提到了帝王蝶数量减少的问题，因此接下来的内容很可能会讨论我们可以做些什么来保护这些蝴蝶。选项A和B虽然可能与环境保护相关，但不如选项C直接关联到文章的主题。
