Why Does the Equilibrium Quantity Change When There Is a Decrease

Why does the equilibrium quantity change when there is a decrease in demand?

A) A shortage leads to a lower price, and a higher price increases quantity supplied and decreases quantity demanded.
B) A surplus leads to a lower price, and a lower price increases quantity supplied and decreases quantity demanded.
C) A shortage leads to a higher price, and a higher price increases quantity supplied and decreases quantity demanded.
D) A surplus leads to a lower price, and a lower price decreases quantity supplied and increases quantity demanded.