Answer
$\sqrt x + 1$
Work Step by Step
f o g o h, given $f(x) = \sqrt{1-x}$ $g(x) = 1-x^2$, $h(x) = 1 + \sqrt x$
$f(g(h(x)))$ = $f(g(1+ \sqrt x))$ =$f(1-(1+\sqrt x)^{2})$ = $f(-2\sqrt x - x)$
$f(-2\sqrt x - x)$ = $\sqrt{1- (-2 \sqrt x - x)}$ = $\sqrt {(\sqrt x + 1)}^2$ = $\sqrt x + 1$