The flow will take place

Question

Point A of head H_A is at a higher elevation than point B of head H_B. The head loss between these points is H_L. The flow will take place    

(a) Always form A to B

(b) From A to B if H_A= H_B + H_L

(c) From B to A if H_Z + H_L=H_B

(d) From B to A if H + H_L=H_A