Which statement is true for all functions f(x)?

A. The graph of f(x) + k is the graph of f(x) shifted left or right by | k | units
B. The graph of -f(x) is the graph f(x) reflected over the x-axis
C. The graph of f(kx) is the graph of f(x) shifted left or right by | k | units
D. The graph of -f(x) is the graph of f(x) reflected over the y-axis