Let $$a, b \epsilon R$$ and $$f: R \rightarrow R$$ be bedefined by $$f(x) = a \cos (\mid x^3 - x \mid) + b \mid x \mid \sin(\mid x^3 + x \mid)$$. Then f is

A

differentiable at x = 0 if a = 0 and b = 1

B

differentiable at x = 1 if a = 1 and b = 0

C

NOT differentiable at x = 0 if a = 1 and b = 0

D

NOT differentiable at x = 1 if a = 1 and b = 1