Which one of the following is the vector? a) Kinetic energy b) Pressure c) Rate of change of momentum d) Density

The answer is c) Rate of change of momentum. This is because a vector is a quantity that has both magnitude and direction. The rate of change of momentum, also known as force, has both these properties: it has a magnitude (how much momentum is changing) and a direction (the direction in which the momentum is changing). On the other hand, kinetic energy, pressure, and density are scalar quantities, meaning they only have magnitude and no direction.