What is the relationship between a planet's distance from the sun and the length of its year?
A. The closer the planet is to the sun, the longer its year.
B. The farther the planet is from the sun, the longer its year.
C. A year on each inner planet is the same length; it is shorter than a year on an outer planet.
D. A year on each outer planet is the same length; it is shorter than a year on an inner planet.