Determine if the function f(x)=x is differentiable at x = 0. If not, identify why. a.) f(x)=x is not differentiable at x = 0 because f(0) is not defined. b.) f(x)=xis differentiable at x=0. c.) f(x)=x is not differentiable at x = 0 because f'(0) is not defined. d.) f(x)=x is not differentiable at x = 0 because lim x does not exist. +0+x