Recall that the graph of h(x) translated n units to the right is the graph of h(x-n).
Now, notice that the given graph is the graph of the function f(x)=x translated 1 unit to the right, therefore the given graph is the graph of f(x-1).
Setting f(x+k)=f(x-1), since the graph is a line we get that:
[tex]x+k=x-1.[/tex]
Subtracting x from the above equation we get:
[tex]k=-1.[/tex]
Answer: First option.
