  We prove that in the infinite speed-of-light limit (i.e., non-relativistic
and subhorizon limits), the relativistic fully nonlinear cosmological
perturbation equations in two gauge conditions, the zero-shear gauge and the
uniform-expansion gauge, exactly reproduce the Newtonian hydrodynamic
perturbation equations in the cosmological background; as a consequence, in the
same two gauge conditions, the Newtonian hydrodynamic equations are exactly
recovered in the Minkowsky background.
