Answer
$x+2\sqrt {5x}+5$
Work Step by Step
Use special formula $(a+b)^2=a^2+2ab+b^2$.
We have $a=\sqrt x$ and $b=\sqrt 5$.
$(\sqrt{x}+\sqrt5)^2=(\sqrt{x})^2+2(\sqrt x)(\sqrt 5)+(\sqrt 5)^2$
Simplify.
$=x+2\sqrt {5x}+5$
Hence, the correct answer is $x+2\sqrt {5x}+5$.
