The property of steam function ψ is :

• A. ψ is constant everwhere on any stream line
• B. the flow around any path in the fluid is zero for continuous flow
• C. the rate of change of ψ with distance in an arbitrary direction, is proportional to the component of velocity normal to that direction
• D. the velocity vector may be found by differentiating the stream function
• E. all the above.