Answer:
C - 0 meters
Explanation:
Displacement is the difference in where you started and where you end up. If Bill starts at his house and ends at his house, there was no change in position, meaning Bill had no displacement. In math this would be
400 + (-400) = 400 - 400 = 0
assuming he runs in the positive direction and then in the negative direction. Either way you put it, it still ends up as 0
