The Black Death was a huge plague spread by Rats that was very contagious, it devastated Europe and killed many people, once it was done away with new tides turned and new foot holds of power proceeded forward due to knew tech, and different method of thinking.
The quantity demanded rises and this is how falling prices affect supply. The correct option among all the options that are given in the question is the third option. People will try to buy more of the product as the product is available at a much cheaper rate. This way the demand of the product in the market will rise.