Let $f:\mathbb{R}\to\mathbb{R}$ defined by $f(x)=x^3-x^2+(x-1)\sin x$ and $g:\mathbb{R}\to\mathbb{R}$ be arbitrary. Let $fg$ be the product function. Number of correct statements: A) If $g$ is discontinuous at $x=1$, then $fg$ can never be differentiable at $x=1$. B) If $fg$ is differentiable at $x=1$, then $g$ is continuous at $x=1$. C) If $fg$ is differentiable at $x=1$, then $g$ must be differentiable at $x=1$.