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Although (虽然) all birds may not look the same, birds have certain things in common (共同的). All birds are warm-blooded. This means that their body temperature (温度) always stays the same. A bird’s body is covered with feathers (羽毛). All birds have two wings. Birds can see very well. They can’t move their eyeballs like people do, so they have to turn their heads to look at something. There are more than 9,000 species (物种) of birds in the world.
1．All birds are warm-blooded.2．Some birds have two wings.
3．Birds can’t see very well.
4．There are only 9,000 kinds of birds in the world.
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
