inverses

Which of the following functions have inverses? Note that the domain of each function is also given. A. $a(x) = \sqrt{2 - x},$ $x \in (-\infty,2].$ B. $b(x) = x^3 - x,$ $x \in \mathbb{R}.$ C. $c(x) = x + \frac{1}{x},$ $x \in (0,\infty).$ D. $d(x) = 2x^2 + 4x + 7,$ $x \in [0,\infty).$ E. $e(x) = |x - 2| + |x + 3|,$ $x \in \mathbb{R}.$ F. $f(x) = 3^x + 7^x,$ $x \in \mathbb{R}.$ G. $g(x) = x - \frac{1}{x},$ $x \in (0,\infty).$ H. $h(x) = \frac{x}{2},$ $x \in [-2,7).