The correct answer is D. Force and velocity.
The dimensions of force are $MLT^{-2}$ and the dimensions of velocity are $LT^{-1}$. Therefore, the dimensions of force times velocity are $ML^{2}T^{-3}$.
The dimensions of mass are $M$, the dimensions of power are $ML^{2}T^{-3}$, and the dimensions of energy are $ML^{2}T^{-2}$. Therefore, none of the other options could be the product of two quantities with the correct dimensions.
Here is a more detailed explanation of each option:
- Option A: Force and pressure. The dimensions of force are $MLT^{-2}$ and the dimensions of pressure are $ML^{-1}T^{-2}$. Therefore, the dimensions of force times pressure are $ML^{2}T^{-4}$. This is not the correct answer because the dimensions of the product are not $M^{2}L^{2}T^{-3}$.
- Option B: Mass and power. The dimensions of mass are $M$ and the dimensions of power are $ML^{2}T^{-3}$. Therefore, the dimensions of mass times power are $ML^{3}T^{-3}$. This is not the correct answer because the dimensions of the product are not $M^{2}L^{2}T^{-3}$.
- Option C: Energy and velocity. The dimensions of energy are $ML^{2}T^{-2}$ and the dimensions of velocity are $LT^{-1}$. Therefore, the dimensions of energy times velocity are $ML^{3}T^{-3}$. This is not the correct answer because the dimensions of the product are not $M^{2}L^{2}T^{-3}$.
- Option D: Force and velocity. The dimensions of force are $MLT^{-2}$ and the dimensions of velocity are $LT^{-1}$. Therefore, the dimensions of force times velocity are $ML^{2}T^{-3}$. This is the correct answer because the dimensions of the product are $M^{2}L^{2}T^{-3}$.