Which of the following statements is true? a) although the planets orbit the sun, our solar system does not itself move in an orbit. b) our solar system follows an orbit through the milky way galaxy that takes millions (but not hundreds of millions) of years to complete. c) our solar system follows an orbit through the milky way galaxy that takes hundreds of millions of years to complete. d) our solar system is at the center of the milky way galaxy, which follows an orbit through the universe that takes billions of years to complete.