A planet moves around the Sun in an elliptical orbit. Which one of the following assertions about the planet’s linear speed is correct according to Kepler’s laws?
(a) The planet moves with uniform speed throughout its orbit.
(b) The planet moves fastest at perihelion and slowest at aphelion.
(c) The planet moves fastest when it is farthest from the Sun and slowest when it is closest.
(d) The planet moves with equal maximum speed at perihelion and aphelion and is slowest halfway between them.