JEE Math Practice Question

Let K be the set of all real values of x where the function f(x) = sin |x| – |x| + 2(x – $$\pi $$) cos |x| is not differentiable. Then the set K is equal to :

1. A.{0, $$\pi $$}
2. B.$$\phi $$ (an empty set)
3. C.{ r }
4. D.{0}