单元自测试卷八年级英语下学期人教版
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（
C
）4. How far do monarch butterflies travel?
A. 400 kilometers.
B. 40,000 kilometers.
C. 4,000 kilometers.
D. 4 kilometers.
答案：C
解析：根据文中“Every year, millions of monarch butterflies fly up to 4,000 kilometers from Canada and the United States to Mexico.”可知，帝王蝶飞行的距离是4000公里，C选项正确。
（
B
）5. How do monarch butterflies find their way to Mexico?
A. By following other butterflies.
B. By using the sun and Earth's magnetic field.
C. By asking humans for help.
D. By covering trees and making them look orange.
答案：B
解析：文中明确提到“Scientists believe they use the sun and Earth's magnetic field to find their direction.”，说明帝王蝶通过太阳和地球磁场辨别方向，B选项正确。
（
B
）6. Why are monarch butterflies important?
A. Because they make honey.
B. Because they pollinate flowers.
C. Because they eat harmful insects.
D. Because they plant milkweed.
答案：B
解析：由“Monarch butterflies are important because they pollinate flowers.”可知，帝王蝶的重要性在于它们能给花授粉，B选项正确。
（
A
）7. ______ is the only plant for monarch caterpillars to eat.
A. Milkweed
B. Orange
C. Flower
D. Potato
答案：A
解析：根据“People are planting milkweed, the only plant monarch caterpillars eat”可知，马利筋是帝王蝶幼虫唯一的食物，A选项正确。
