When a planet moves in an elliptical orbit around a star, the mechanical energy of the system is conserved. The mechanical energy is given by the sum of the kinetic energy and the potential energy.
When the planet is closer to the star, the potential energy is lower than when the planet is farther away from the star. To compensate, the kinetic energy grows bigger when the planet is closer to the star, and it gets smaller when the planet is farther away from the star.
Since the kinetic energy is proportional to the square of the speed of the planet, then, the planet moves faster when it is closer to the star and slower when it is farther from the star.
Therefore, both options C and D are correct: a planet moving in an elliptical orbit moves slower when it is farther away from the Sun and faster when it is closer to the Sun.
Then, the answer is:
