Which of the statements are correct?

Question

Consider the following statements about velocity potential:            

1. Velocity potential is a vector function similar to stream function

2. It is a fully three dimensional function and not limited to two coordinates.

3. Velocity potential does not exist at stagnation points

4. Velocity potential exists only if the flow is irrotational

Which of the statements are correct?

(A) 1, 2 and 3              (B) 1, 2 and 4

(C) 1, 3 and 4              (D) 2, 3 and 4