Average speed = (total distance covered) / (total time to cover the distance) .
Total distance = (80 + 50 + 40) = 170 km
Total time = (1 + 0.5 + 0.5) = 2 hours
Average speed = (170 km) / (2 hrs) = 85 km/hr .
With time, momentum increases as it builds speed assuming their is nothing in the way to stop it. Based on the graph, you can see that example being displayed as the line on the graph gets higher
D
Its D i think because it doesnt refer to any other things