19) B

A straight line on the distance-time graphs show us constance velocity (no change in velocity). Since there is not change in velocity, acceleration must be zero.
So R and S are definitely wrong.

A straight line on velocity-time graphs shows us constant acceleration.
Equation for acceleration = (final velocity – initial velocity) ÷ time
Acceleration in P = (10 – 0)/24 = 0.4
Acceleration in Q = (60 – 10)/20 = 2.5 (almost 2.4)

Hence, the answer is B (Q only).