How is the graph of g(x) = f(kx) related to the graph of f when k = 5?

A. The graph of g is a horizontal stretch of the graph of f.
B. The graph of g is a vertical stretch of the graph of f.
C. The graph of g is a horizontal compression of the graph of f.
D. The graph of g is a vertical compression of the graph of f.

When we multiply a constant positive number to the domain of the function, the variations on the "x" axis have a greater impact on the "y" axis. In this case for the original function every variation on the "x" axis would imply on a variation of the "y" axis, but on the new function where we have "f(kx)" with "k = 5", every variation on the "x" axis implies on 5 times the original value of the variation on the "y" axis, so for a smaller interval in the "x" axis we have more information about the "y" axis than before. Therefore, the graph gets compressed horizontally.