A change to the inside of the function notation is always a left/right or horizontal change to the graph.
Answer: A
Subtracting 5 actually shifts the graph to the right by 5 units. It's counter-intuitive and there are many ways to explain why it's the opposite of what you think it'd do, but it is a shift to the right by 5 units.
PS
A change outside the f(x) notation is an up/down or vertical change to the graph.