The SI unit of a physical quantity is Pascal-sec. The dimensional formula of this quantity will be

We need to find the dimensional formula of a physical quantity whose SI unit is Pascal-second (Pa·s).

Write the dimensional formula of Pascal.

Pascal is the unit of pressure:

$$[\text{Pa}] = \frac{[\text{Force}]}{[\text{Area}]} = \frac{MLT^{-2}}{L^2} = ML^{-1}T^{-2}$$

Multiply by the dimension of time.

$$[\text{Pa} \cdot \text{s}] = ML^{-1}T^{-2} \times T = ML^{-1}T^{-1}$$

This is the dimensional formula of dynamic viscosity (coefficient of viscosity).

The correct answer is Option C.