This process of elimination seems to leave very few planets on which earthlike life might be found. However, even if life could exist on only one planet in a million, there are so many billions of planets that this would still leave a vast number on which life could exist.
　　1. Astronomers believe that matter in different parts of the universe
　　A) has different laws.
　　B) has one common law.
　　C) shares the same laws
　　D) shares no common law.
　　2. The existence of life depends on all of the following factors EXCEPT
　　A) the right amount of atmosphere.
　　B) our own solar system.
　　C) steady heat and light.
　　D) the right distance from the sun.
　　3. Which of the following statements is INCORRECT?
　　A) The planet must be as big and heavy as the earth.
　　B) Proper conditions are essential to the existence of life
　　C) Double stars can provide steady light and heat.
　　D) The distance between a planet and its sun should be right.
　　4. What kind of planet might NOT support life?
　　A) Most of the planets of the stars.
　　B) Stars similar to our sun.
　　C) Planets similar to the earth.
　　D) Planets with proper conditions.
　　5. At the end of the passage the author suggests that
　　A) it is impossible for life to exist on planets.
　　B) earthlike life could only exist on a few planets.
　　C) life could exist on only one planet in a million.
　　D) life could exist on a great number of planets.
　　KEY: CBCAD