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Find two functions, $f$ and $g$ such that $f(g(x))=\sqrt{x^2+1}$.

$f(x) = \sqrt{x+1}$, $g(x) = x^2+1$

$f(x) = x^2+1$, $g(x) = \sqrt{x}$

$f(x) = \sqrt{x}+1$, $g(x) = x^2$

$f(x) = \sqrt{x}$, $g(x) = x^2+1$