For one dimensional flow of an incompressible fluid in unsteady state in x-direction, the continuity equation is given by_______________?
A. ∂u/∂x = 0
B. ∂(ρu)/∂x = 0
C. (∂u/∂x) = – (∂ρ/∂t)
D. ∂ρ/∂t = 0