(A). x|x| is continuous, differentiable and strictly increasing in (−1,1) .
(B). √|X| is continuous in (−1,1) and not differentiable at x=0.
(C).
x+[x] is strictly increasing in (−1,1) and
discontinuous at x=0⇒ not differentiable at
x=0.
(D). |x−1|+|x+1|=2 in (−1,1)
⇒ the function is continuous and differentiable in (−1,1) .