Identify the correct statements about density, Reynolds number, and hydrostatic pressure in the approximate Navier-Stokes equation for creeping flow in very small gaps and channels of a lubricated bearing.
a) The hydrostatic pressure term is negligible.
b) Absence of free-surface effects allows us to use modified pressure instead of the physical pressure.
c) The hydrostatic pressure term cannot be neglected.
d) Density is no longer needed in the creeping flow approximation.
e) Density plays a very important role in the creeping flow approximation.