Well? How many of you got the correct answer??
Which is...............0!! Zero!!
The only time the arrow will have a speed of Zero (ie, when it is stopped/stationary) is when it hits the ground again!!! So it's height will be zero!!
Any other answer is WRONG, never mind what Mark scheme said! The arrow will NOT stop until its the ground again! This idea of some mythical point in the air where the arrow is momentarily not moving is rubbish. It's ALTITUDE may not be changing. It, for an instant, may not be getting any higher or lower, but IT IS STILL MOVING FORWARD AND WILL CONTINUE TO DO SO UNTIL IT HITS THE GROUND!!! Then, and only then, will it stop!