A skateboarder rolls forward at constant speed on a smooth, level surface and tosses a ball straight upward relative to herself. She wants to predict where the ball will land most easily. Which reference frame would make that prediction require the fewest calculation steps?
a) A frame fixed to the ground
b) A frame moving at half the skateboarder’s speed in the same direction
c) A frame moving with the skateboarder
d) The ball’s instantaneous rest frame at the moment of release