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问题 单项选择题

Removing which will extinguish a fire?（）.

A.Nitrogen

B.Carbon dioxide

C.Sodium

D.Oxygen

答案

参考答案：D

单项选择题

根据《到港后交单

A．承兑后付款时交单
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单项选择题

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.

The main idea of this passage is that________.

A．there are life-supporting characteristics on the Earth

B．the Earth is predominantly water

C．the Earth has no common characteristics with other planets

D．the Earth is the only planet with a moon
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