(a) The value of velocity is greater when inclination of x-t graph from the time-axis is greater. The inclination of x-t graph of object B is the highest so B is moving at the fastest speed.

(b) All three x-t graph do not meet at any one point. Hence A, B and C will never be at the same point on the road.

(c) On the distance axis:
7 small boxes = 4 km
∴ 1 small box = 4/7 km
Initially, object C is 4 blocks away from the origin.
∴ initial distance of object C from origin = 4×(4/7)

=16/7
Distance of object C from origin when B passes A = 4/7×16

=64/7
Distance covered by C=64/7−16/7

=(64−16)/7

=48/7=6.85 km
Hence, the total distance covered by C when B passes A is 6.85 km.

(d) Distance covered by B at the time it passes C = 9 boxes
Distance travelled by B when it passes C = 4/7×9

=36/7=5.143 km
Hence, B has travelled a distance of 5.143 km when B passes C.