單元自測試卷八年級英語下學期人教版
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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：根據文中“Every year, millions of monarch butterflies fly up to 4,000 kilometers from Canada and the United States to Mexico.”可知，帝王蝶飛行的距離是4000公里，C選項正確。
（
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：文中明確提到“Scientists believe they use the sun and Earth's magnetic field to find their direction.”，說明帝王蝶通過太陽和地球磁場辨別方向，B選項正確。
（
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們能給花授粉，B選項正確。
（
A
）7. ______ is the only plant for monarch caterpillars to eat.
A. Milkweed
B. Orange
C. Flower
D. Potato
答案：A
解析：根據“People are planting milkweed, the only plant monarch caterpillars eat”可知，馬利筋是帝王蝶幼蟲唯一的食物，A選項正確。
