Question

If f(x) = x2, which of the following describes the graph of f(x - 1)?
a.The graph of f(x - 1) is a vertical shift of f(x) = x2 one unit up.
b.The graph of f(x - 1) is a vertical shift of f(x) = x2 one unit down.
c.The graph of f(x - 1) is a horizontal shift of f(x) = x2 one unit to the right.
d.The graph of f(x - 1) is a horizontal shift of f(x) = x2 one unit to the left.
help pleaseeee .