For exponential functions, if you add a positive number to the exponent you will shift the graph to the left. Similarly, if you subtract a positive number to the exponent you will shift the graph to the right.
Here it states that k < 0, which means it is negative. Therefore we know that we are subtracting from the exponent. So we know that f(x) is shifted to the right of graph g(x).
Hence, the answer is B.