As viewed from space.the Earth's distinguishing characteristics are its blue waters and white clouds.Enveloped bu an ocean of air consisiting 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,the Earth is the third planet from the sun and the fifth largest planet in the solar system.Tts rapid 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 san and other stars.Most meteors burn up in the Earth's atmosphere before the can strike the surface.The planet's active geological processed 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.
1 The main idea of the passage is that
A there are lofe-supporting characteristics on the earth
B the earth is predominantly water
C the earth has no common chatacteristics with other planets
D the earth is the only planet with a moon
2 this selection leads one to believe that
A the earth never gets hit by meteors
B the earth always gets hit by meteors
C the earth was hit by meteors some time in the past
D the earth may be bombarded by meteors in the near future