Which graph represents the function?

I think you mean

f(x)= Sqrt (x-1)  becasue none of them are   f(x)= Sqrt x-1

f(x)= Sqrt (x-1)

you know   Sqrt (4) = 2

and

f(x)= Sqrt (5-1)=sqrt(4)

so  lets think about  x=5 

f(5)= sqrt(5-1)  =   sqrt4  =  2

So (5,2) must be a point on the graph.

So which is the correct graph?

Does the last graph have the point (5,2) on it?