The conventional demand curve is that the lower the price, the higher the quantity demanded. This relationship follows the law of demand. It states that the quantity demanded will drop as the price rises, ceteris paribus, or  “all other things being equal.” The relationship between quantity and
price will follow the demand curve as long as the four determinants of demand don’t change. These determinants are:
1. Price of related goods or services. 
2. Income of the buyer.
3. Tastes or preferences of the buyer,
4. The expectation of the buyer, especially about future prices.

The true answer is A.