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Many animals migrate（迁徙）. 1. They travel in big groups from one place to another. Some animals migrate when the weather changes. Others set off to find new food and water. 2. Lots of animal migrations take place in Africa. Here, you can read about three of them.
As the seasons change, zebras（斑马）travel in large groups. They make the trip year after year. 3.斑马为什么走那么远？They are looking for better grass to eat.
Wildebeests（牛羚）are always on the move. They travel by day and by night. Their journey can take them through rivers and streams.4.牛羚擅于游泳。But crossing the water is dangerous.
Flamingos（火烈鸟）fly together in the shape of V. They head for Africa’s salt flats（盐滩）. A salt flat is an area of water that has dried up. During the rainy season, a salt flat becomes a wetland. 5. It’s a great living place for flamingos.
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同类型试题
y = sin x， x∈R， y∈[–1，1]，周期为2π，函数图像以 x = (π/2) + kπ 为对称轴
y = arcsin x， x∈[–1，1]， y∈[–π/2，π/2]
sin x = 0 ←→ arcsin x = 0
sin x = 1/2 ←→ arcsin x = π/6
sin x = √2/2 ←→ arcsin x = π/4
sin x = 1 ←→ arcsin x = π/2
y = sin x， x∈R， y∈[–1，1]，周期为2π，函数图像以 x = (π/2) + kπ 为对称轴
y = arcsin x， x∈[–1，1]， y∈[–π/2，π/2]
sin x = 0 ←→ arcsin x = 0
sin x = 1/2 ←→ arcsin x = π/6
sin x = √2/2 ←→ arcsin x = π/4
sin x = 1 ←→ arcsin x = π/2
