Calculus 10th Edition

The graph of $3^x-1$ is just the graph of $3^x$ shifted vertically down by one unit which is (b). Let's find out the crucial limits to get some more insight. $\lim\limits_{x \to -\infty}3^{x}-1 = -1$ $\lim\limits_{x \to \infty}3^{x}-1=\infty$ both of which are same as that of the graph in (b)