736. given that f is a real-valued differentiable function such that ff') <0 for all real z, it follows that (a) f(r) is an increasing function; (b) f(r) is a d

736. Given that f is a real-valued differentiable function such that ff') <0 for all real z, it follows that (A) f(r) is an increasing function; (B) f(r) is a decreasing function; (C) If(r)| is an increasing function; (D) |f(r)| is a decreasing function.