Answer: A
Zero yard.
Explanation:
Given that that John lives on a square block that is 180 yards per side, and in the evenings, he walks with his dog around the block for a little exercise.
Constant speed does not necessarily mean constant velocity.
If John walks once around the block, his final displacement will be equal to zero yard.
Because displacement is the distance between the initial and final position of an object. When an object returns to its original position, displacement will be therefore equal to zero yard.
Therefore, the best answer is option A
