30 Points PLEASE ANSWER ASAP

The graph of f(x) = (0.5)x is replaced by the graph of g(x) = (0.5)x − k. If g(x) is obtained by shifting f(x) down by 3 units, then what is the value of k? (1 point)
k = −3
k equals negative one third
k equals one third
k = 3