The rule of a reflection about the x-axis is given by
[tex]f(x)\longrightarrow-f(x)[/tex]in our case,
[tex]f(x)=\sqrt[]{x}[/tex]then, by reflecting this function about the x-axis, we get
[tex]f(x)=\sqrt[]{x}\longrightarrow F(x)=-\sqrt[]{x}[/tex]therefore, the answer is option D.