An 80-kg person is holding a 20-kg box just outside of his spaceship. The person is a few meters away from the spaceship, and is not moving with respect to the spaceship. If the person pushes the box in a direction away from the spaceship,

• (a) the person accelerates toward the spaceship, with less acceleration than the box,
• (b) the person accelerates toward the spaceship, with more acceleration than the box,
• (c) the acceleration of the person is zero, or
• (d) the person experiences an equal and opposite acceleration toward the spaceship.