Can you match the teacher's comments to the justifications? So, before I even look at what the students wrote, you might say, hey, look, I can just look at this and see that h is increasing when x is greater than zero. But just by looking at the graph of h, that by itself is not a calculus-based justification. We're not using calculus. We're just using our knowledge of what it means for a graph to be increasing. In order for it to be a calculus-based justification, we should use calculus in some way, and so maybe use the derivative in some way. Now, you might recognize that you know that a function is increasing if its derivative is positive.