What is the momentum of an object of mass 'm', moving with a velocity 'v' ?

The momentum is defined as the product of the mass and the velocity. 

The expression for the momentum is $\mathrm{p}=\mathrm{mv}$ ,

Here, $\mathrm{p}$ is the momentum, $\mathrm{m}$ is the mass and $\mathrm{v}$ is the velocity of the object.

Hence, option 4 is the correct answer.