analytic function

Question

MCQ:

let f(z)= u(x,y) + iv(x,y).  Indicate the v(x,y) functions for which f(z) may be analytic.

1, 4(x^2-y^2)

2, 4(x^2+y^2)

3, e^(4x)*sin(4y)

4, e^(4x)*cos(4y)

5, log(x^2-y^2)

6, log(x^2+y^2)