What is the main purpose of the lecture? [originaltext]Listen to part of a lectu

Listen to part of a lecture in an environmental science class. (P = Professor, C = Carly)
P: Now, over the next few weeks, we’re going to focus on carbon and its role in what’s known as the greenhouse effect. Everyone knows what that is, right? But let’s make sure anyway. Yes, Carly?
C: The greenhouse effect is when gases in Earth’s atmosphere act like the glass in a greenhouse or hothouse. They trap in heat which warms up the Earth.
P: Gases like?
C: Water vapor? Carbon dioxide?
P: Right, carbon dioxide. We hear a lot about carbon these days, no? Carbon emissions, carbon burning, leaving a carbon footprint. So, it’d be easy to assume that any form of carbon burning is necessarily a bad thing. But the fact is it’s not quite that simple. So, we’re going to focus today on the difference between good, bad and well, and not-so-bad, potentially okay carbon burning.