There are two given physical quantities $$A=\frac{F}{\rho v^2D}$$ and $$B=\frac{\rho vD}{\eta}$$ where $$F$$ is force, $$\rho$$ is density, $$D$$ is diameter, $$v$$ is velocity and $$\eta$$ is the coefficient of viscosity. Which of the two $$A$$ and $$B$$ is or are dimensionless?

A

$$A$$

B

$$B$$

C

neither $$A$$ nor $$B$$

D

both $$A$$ and $$B$$