Final answer:
To ensure a horizontally thrown football hits the target, the speed of the throw should be B) decreased to give the football more time to reach the target.
Step-by-step explanation:
To ensure that a horizontally thrown football hits the target instead of going past it, the most effective adjustment would be to B) Decrease the speed of the throw to give the football more time to reach the target. When the speed of the throw is reduced, the football will have a longer flight time, allowing it to cover the necessary distance to reach the target.
Increasing the speed of the throw (A) would actually cause the football to travel farther and potentially overshoot the target. Adjusting the height of the throw, either by raising it (C) or lowering it (D), would affect the vertical trajectory of the football but not the horizontal distance it travels.