In a comet-Sun system, the position of the comet closest to the Sun is called perihelion, and the position of the comet farthest from the Sun is called aphelion. The two quantities that both have their highest values when the comet is in perihelion are:
(a) the acceleration and the potential energy of the comet;
(b) the speed and the potential energy of the comet-Sun system;
(c) the speed and the acceleration of the comet;
(d) the acceleration and the total energy of the comet-Sun system.