There is no air________water on the moon．

1. A.
   so
2. B.
   but
3. C.
   and
4. D.
   or

He ________ there is no air or water on the moon.

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　　The sounds we hear on the earth are carried by the air. Since there is no air on the moon, people who get to the moon must talk to each other by radio. The dust（灰尘）in the earth's air, though very little, scatters（散射）he sunlight. This makes the earth's daytime sky blue and the shadows（阴影）are not completely dark. But on the moon, the sky is always black. You would be able to see stars in the daytime. Sunny places on the moon would be very, very bright. But the shadows would be almost black. The moon has no air or wind to carry the sun's heat. So it can get hot enough to boil（煮开）water in the places where the sun is shining straight down.

[　　]

[　　]

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A．the air around is a blue gas

B．there is dust on the earth

C．of the fact that the sunlight is blue

D．there is air around and the dust in the air scatters the sunlight

[　　]

A．The shadows on the moon would be nearly black.

B．All the sunny places of the moon can become so hot as to boil water.

C．The moon has no air and no wind.

D．Even in the daytimes stars could be seen on the moon.