Answer
The acceleration is maximum when the orbiting body is closest to the central body, i.e., at perihelion for a planet orbiting the sun.
The acceleration is minimum when the orbiting body is farthest from the central body, i.e., at aphelion for a planet orbiting the sun.
Work Step by Step
The planet's acceleration is the net force on it, divided by the mass of the planet.
a. The net force, in this case, gravity, is strongest when the orbiting body is closest to the central body.
b. The net force, in this case, gravity, is weakest when the orbiting body is farthest from the central body.
