9. In a competitive market, an increase in demand; a- will lead to an increase in both the equilibrium price and quantity. Will lead to an increase in price but decrease in supplied quantity. C- will lead to decrease in price but increase in supplied quantity. will lead d to a slowdown in the economy.

In a competitive market, an increase in demand will lead to an increase in both the equilibrium price and quantity. This is because as demand increases, suppliers are willing to supply more at higher prices to meet the increased demand, resulting in a higher equilibrium price and quantity. Therefore, the correct answer is option A.