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What is the sky? Where is it? How high is it? What lies above? They are difficult to answer, aren’t they?
Is the sky blue? The sky has no color. Is the sky full of air? We know that there is air around the world. When planes fly, they need air to lift their wings. Planes cannot fly very high because when they go higher, the air gets thinner. If we go far enough from the earth, we find there is no air.
Perhaps we can answer some of our questions now. What is the sky? Nothing. Where is it? It is all around the world. The sky is space (空间). In this space there is nothing but the sun, the moon and all the stars.
1．—What is the sky? ( )—_______________
| A．It is the clouds. | B．It is the whole world. | C．It is space. | D．It is air. |
| A．is blue | B．has no colour |
| C．is colourful | D．is different colour at the different time of the day |
| A．there will be less and less air to lift their wings |
| B．the flying machine is not good enough |
| C．the pilot will be afraid if he flies too high |
| D．there will not be enough air for the pilot to breathe |
| A．is nothing | B．is air everywhere |
| C．is the earth | D．is the sun , the moon and all the stars |
| A．机身 | B．机翼 | C．机头 | D．机尾 |
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
