A superadditive function $f(\cdot)$ satisfies the following property $f\left(x_{1}+x_{2}\right) \geq f\left(x_{1}\right)+f\left(x_{2}\right)$.Which of the following functions is a superadditive function for $x>1 ?$
(A) $e^{x}$
(B) $\sqrt{x}$
(C) 1/x
(D) $e^{-x}$
A superadditive function $f(\cdot)$ satisfies the following property $f\left(x_{1}+x_{2}\right) \geq f\left(x_{1}\right)+f\left(x_{2}\right)$.Which of the following functions is a superadditive function for $x>1 ?$
(A) $e^{x}$
(B) $\sqrt{x}$
(C) 1/x
(D) $e^{-x}$