[单项选择]The 15 plates of the Earth are formed from ______.
A. the oceanic crusts and continental crests
B. the crusts and the mantle
C. the crusts and the top and solid part of the mantle
D. the continental crusts and the solid part of the mantle

[单项选择]The 15 plates of the Earth are formed from________.
A. the oceanic crusts and continental crusts
B. the crusts and the mantle
C. the crusts and the top and solid part of the mantle
D. the continental crests and the solid part of the mantle

[单项选择]Clouds are formed from ______.
A. water vapor
B. evaporation
C. the hydrologic cycle
D. groundwater

[单项选择]The light from the earth makes it possible for us to be able to see the parts of the moon which would otherwise be dark.
A. 来自地球的光使我们能够明白月球上的一些地方是暗的。
B. 来自地球的光使月球上的一些地方成为亮的，另外一些地方是暗的。
C. 来自地球的光使我们能够看到月球上的一些地方，但是月亮的另一部分是黑暗的。
D. 来自地球的光使我们能够看到月球上的一些地方。否则的话，这些地方是黑暗的。

[单项选择]Seen from space, our earth, with water covering 70% of its surface, appears as a “blue planet”.
A. 如果从太空中看地球的话，地球像一个蓝色的行星，而且地球的表面70%都是水。
B. 地球表面的70%都被水覆盖着，从太空中看地球，它就像一颗蓝色的行星。
C. 从太空上看我们的地球，它表面的70%都被水覆盖着，看上去像一颗蓝色的行星。
D. 从太空中看到地球的表面的70%都是水，它是一个蓝色的行星。

[单项选择]

As viewed from space, the Earth’s distinguishing characteristics are its blue waters and white clouds. Enveloped by an ocean of air consisting of 78% nitrogen and 21% oxygen, the planet is the only one in our solar system known to harbor life. Circling the Sun at an average distance of 149 million km (93 million miles), the Earth is the third planet from the Sun and the fifth largest planet in the solar system. Its rapid spin and molten nickel-iron core give rise to an extensive magnetic field which, coupled with the atmosphere, shields us from nearly all of the harmful radiation coming from the Sun and other stars. Most meteors burn up in the Earth’s atmosphere before they can strike the surface. The planet’s active geological processes have left no evidence of the ancient pelting it almost certainly received soon after it was formed. The Earth has a single natural satellite -- the Moon.

Approximately how much of the Earth's atmosphere is nitrogen（）
A. One-fourth.
B. One-half.
C. Three-fourths.
D. All of it.

[单项选择]（） from space, our earth, with water covering 70% of its surface, appears as a "blue planet"
A. Seeing
B. To be seen
C. Seen
D. Having seen

[单项选择]It can be seen from the passage that the earth's supply of natural medicines
A. may never be exhausted.
B. may be dropping rapidly.
C. is surprisingly big.
D. is as rich-as ever.

[单项选择]The moon is ______ away from the earth.
A. about 384 000 kilometers
B. 240 000 kilometers
C. only 348 000 kilometers
D. about 384 000 meters

[单项选择]______ from space, our earth, with water covering 70% of its surface, appears as a "blue planet ".
A. Seen
B. Seeing
C. To be seen
D. Having seen