The correct choice is A. 0 meters.
If you simply dropped the cannonball and didn't throw it horizontally,
then it'll fall straight down the mast and land on the deck right next to
the mast.
While you were up there holding it, before you dropped it, the cannonball
was moving horizontally, at 2.0 meters/second, along with the rest of the
ship and everything else aboard. It continued doing that after it dropped,
and from the point of view (in the reference frame) of the mast and everyone
on the ship, it fell straight down, parallel to the mast.
Now that we have that question answered, we can proceed to the more-
important ones. I answered the easy one, but YOU'll have to answer these:
==> WHY did you climb the mast carrying a cannonball ?
Have you been drinking sea water or bad rum ?
==> WHY did you drop it, and never even yell "LOOK OUT BELOW !" ?
==> How many formerly-able-bodied souls were injured by the
plummeting cannonball ?
==> What did everybody ELSE yell after the impact ?
==> What did they do to you after they brought you down ?