Explanation

Displacement is the straight-line distance between the start and end points, not the distance travelled. In 60 seconds the athlete completes exactly 3 rounds (60/20) and returns to the starting point, so the displacement after 1 minute is 0 m. In 10 seconds the athlete completes half a round and finishes diametrically opposite the start, so the displacement equals the track's diameter, 100 m. The 300 m figures in the distractors confuse distance covered with displacement.