Nitpick: "If a pen is dropped on A moon"
It doesn't specify Earth's moon. If a pen were dropped on say, Deimos, it might very well appear to do B) for a long moment ;) (Deimos is Mars' outermost moon and too small to retain a round shape. Its gravity is only 0.00256 m/s^2 and escape velocity is only 5.6 m/s. That means you could run off it.)

On the other hand, the word "dropped" effectively gives the game away. Things dropped go DOWN, not up, and they don't float in place. Would be better to say "released".

And now, back to our story...