Answer Happy

Which of the following sets of equations represent pos- sible two-dimensional incompressible flow cases? (a) u=21² + y²-y; v=x²+x(2²-4y) (b) u=2xy-x²y; v = 2xy-y²+x² (c) u=x²+2y; v=x²-yt (d) u = (2x+4y)xt; v = -3(x+y)yt