We have three players today. Each of them will tell us about himself. Let's welcome them.
     Earth(地球):I am the third planet (行星) from the sun. I have one moon (卫星). I have many
mountains. I give a home to lots of plants and animals. I have much water on me.
     Mars(火星):I am the fourth planet from the sun. I am a planet with high mountains. I have two
small moons. People call them Phobos and Deimos. I have a very high mountain. People call it
Olympus Mons.
     Mercury(水星):Well, I am the nearest planet to the sun. I am also the second smallest planet.
I don't have any moons. I am the fastest (最快的) of all the planets when I go around the sun. It
only takes me 88 earth days (One earth day is 24 hours). 

1. The underlined word "them" in the first paragraph refers to (指的是) _______.

A. the three planets        
B. moons
C. 88 earth days            
D. mountains

2. Earth is different from other planets in that_______.

A. it has a moon          
B. it has much water on it
C. it's the only planet of the sun
D. it's the only planet with mountains

3. According to the passage, where can we see the high mountain -Olympus Mons?

A. On the sun.          
B. On Mars.
C. On the earth.        
D. On Mercury.

4. How long does it take Mercury to go around the sun?

A. 24 hours.        
B. 88 hours.
C. 408 hours.        
D. 2112 hours.

5. What can we NOT learn from the passage?

A. Mercury has no moons.
B. Mercury is very near to the sun.
C. Mars goes around the earth.
D. Phobos and Deimos are moons of Mars.