Question

Use complete sentences to describe how measurements of position in two directions (vertical and horizontal) are sufficient enough to describe the position of an object on a flat surface.

Answer 1

Essentially, you can always tell a  thing's position by 3 coordinates. We also say that our world is three-dimentional: it has three dimensions -that's why three coordinates are needed.

If something is on a flat surface, you know its one coordinate (all points on the same surface have the same coordinate) so you only need two more (you can call them vertical and horizontal)