Question: Scientists compared Pluto with other objects in the solar system and found that Pluto is smaller than Earth's moon. This finding caused scientists to question whether Pluto is a planet because

  Options: 
 A. Pluto gets less sunlight than Earth's moon
 B. the other planets are much larger than Pluto
 C. the other planets have moons and Pluto does not
 D. Pluto rotates on its axis and the other planets do not
Answer: B