Mars （火星） is the fourth planet from the sun．It is 141million miles away from the sun．It has two moons．A year on Mars is 687earth-days long．
Mars is about half the size of Earth．Because Mars is smaller than Earth，its gravity （重力） is also less．If you weighed 100pounds on Earth，you'd weigh onlyabout 38pounds on Mars．
Mars'surface looks like a red desert．There are mountains，canyons （峡谷），and crates （火山坑）．There are no rivers oroceans．It is a planet without any liquid （液态） water．It was named by the ancient Romans for their God of War．It is very cold on Mars．Mars is much colder than our planet．The temperature on Mars is 80degrees below zero!That is a lot colder than the North Pole!
Scientists suggest that Mars once had rivers，lakes，and maybe even an ocean．Mars has mountains that are much higher than those on Earth．Mars also has bigger，deeper canyons than Earth's．Some of these are sixty miles long and five or six miles deep．No people could live there．But it's fun to learn about this red planet．Don't you think so？
58．Mars is the planet from the sun．___
A．third
B．fourth
C．fifth
D．sixth
59．Mars is．___
A．the largest planet
B．one-fifth of the Earth
C．about half the size of Earth
D．about the same size as Earth
60．Mars was named after．___
A．the fir
B．a red desert
C．the color of its surface
D．the God of War
61．Which of the following is NOT true according to the passage？___
A．Mars never had rivers or lakes．
B．Mars is much colder than Earth．
C．A man can lift heavier things on Mars than on Earth．
D．Living on Mars for one year means that a person lives for 687days on Earth．
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