f(g(x)) is a composite function:
[tex]f(g(x))=f(\sqrt{x+5})=2\sqrt{x+5}-1[/tex]
Plug in x = 4:
[tex]f(g(4)) = 2\sqrt{4+5}-1=2\sqrt9-1=2\cdot3-1=\boxed{5}[/tex]
so the answer is C.
