【正确答案】 C

【答案解析】[听力原文] Monarch butterflies, the large origin black insects, are common summer sights in northern United States and Canada. They brighten in parks and gardens as they fly among the flowers. What makes monarch butterflies particularly interesting is they migrate, all the way to California or Mexico in back. They are thought to be the only insect that does this. Every year in the late summer, monarch begin their migration to the south, those heading for Mexico go first for the Louisiana Mississippi region. And then they fly to go across Mexico into Texas. Once in Mexico, they establish themselves in one of about 15 sizes in the mountain forth. Each side provides the winter home for millions of monarchs. The butterflies are so numerous that they often cover the entire trees. When spring comes, they began their long journey north. The question is often asked whether every butterfly makes the round trip journey every year. And the answer is no. The average monarch lives about nine month. So when fly the north, they might lay eggs in Louisiana and die. The eggs of that following generation may be found in Kentucky, the eggs of next generation may be in the Kang Michigan. The last generation of the season about the forth may make the journey back in Mexico and restart the cycle. Scientists learn about the monarch butterflies' migration by capturing and placing the identifying tags in the insects. By recapturing the attempt of the monarch and noting where they came from, the next scientist can figure out things like butterfly's age and its routing. What is unique about the monarch butterfly according to the speaker? 本题定位到第三、四句话，第四句中的“the only insect that does this”就是本题题干的出处，而“this”指的是上文提到的它们迁徙的方式。由此得知，令monarch butterflies 独一无二的是它们的迁徙方式，对应选项C。Fixed routes表示固定路线，是对原文“all the way to California or Mexico in back”的概括性改写。