The answer is A: to inform readers about the grandfather's role in creating beet sugar. The speakers say they don't know what grandfather's invention did, but they inform about the result of him managing to turn the beet sugar lighter somehow, which he was able to sell to many buyers, from different places. <em>His creation of beet sugar</em> and and its selling brought him money that made possible for him to buy his freedom.
Unplanned humor is natural, I'd say that's why. Planned humor is often classified as trying to hard so sometimes it seems annoying unlike unplanned humor