帝王蝶的种群有灭绝的危险

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conservation – n. the protection of animals, plants, and natural resources

milkweed – n. type of North American plant that has white juice

migratory – adj. moving from one place to another at different times of the year

endangered – adj. used to describe a type of animal or plant that has become very rare and that could die out completely

species – n. a particular group of things or people that belong together