If $y=\sqrt {x^2+6x+8}$, then the value of $\sqrt {1+iy}+\sqrt {1-iy}$= ?

Question

$\begin{array}{1 1}(A)\sqrt {2(x+4)} \\ (B) \sqrt {(x+4)} \\ (C) \sqrt {2(x+3)} \\(D) \sqrt {(x+3)} \end{array}$