16. Together, the sun and all of the bodies that revolve around it are called
A. the inner planets
C. the solar system
B. the outer planets
D. the galaxy
17. All of the following are inner planets except
A. Earth
B. Saturn
C. Mars
D. Venus
18. Why do planets remain in orbit around the sun?
A. due to the planets' size
C. due to gravity
19. Which planet has extreme temperatures because it has no atmosphere?
B. due to the planets' density
D. due to the planets' features
A. Earth
B. Mercury
C. Jupiter
D. Saturn
20. Which of the following is true?
A. Both the moon and sun orbit Earth.
B. The moon orbits Earth and Earth orbits the sun.
C. The sun orbits the moon and Earth orbits the sun.
D. The moon orbits the sun and Earth orbits the sun.​