The correct answer is A.
When demand increases, the demand curve shifts to the right. This means that at every price, consumers are willing to buy more of the good. As a result, the equilibrium price will increase and the equilibrium quantity will increase.
Option B is incorrect because when demand increases, the equilibrium price will increase, not decrease.
Option C is incorrect because when demand increases, the equilibrium quantity will increase, not decrease.
Option D is incorrect because when demand increases, both the equilibrium price and the equilibrium quantity will increase.