The most basic proposition of the law of demand is that as the price of a good rises, a lower quantity is demanded, or answer C. This is because the law of demand is part of the supply and demand curve - that funky graph that you see with one line going up, one going down, and the point in the middle being where the best quantity for the best price is. When prices are higher, there’s less demand for a product. You see this in reality everywhere.
For example, if there’s a product that is $100 less than another but of the same quality, that cheaper product is probably the more popular one. That’s just the way the world works.