The correct answer is B . Market equilibrium occurs at the price at which the quantity buyers are willing and able to purchase equals the quantity sellers are willing and able to supply. At this equilibrium price there is neither an excess quantity demanded nor an excess quantity supplied, so there is no inherent market pressure for the price to move upward or downward, assuming other factors remain unchanged.
If the prevailing price is below equilibrium, quantity demanded normally exceeds quantity supplied, creating a shortage or excess demand . Competitive pressure then tends to push the price upward. Conversely, when price is above equilibrium, quantity supplied exceeds quantity demanded, producing a surplus or excess supply and downward pressure on price. This means C and D reverse the normal direction of adjustment: excess demand generally pushes prices higher, while excess supply generally pushes prices lower.
“Stable” in B should be understood as equilibrium stability under the assumptions of the model, not a guarantee that an actual market price can never change. Shifts in consumer preferences, income, production costs, technology, expectations or other variables can move the supply or demand curve and establish a new equilibrium.
The official CIRE syllabus expressly lists “Market equilibrium” among the basic economic theories candidates must know within its Market and Company Analysis curriculum.
Study Guide Reference: CIRE Element 5.1 — Basic Economic Theories: market equilibrium, interest rates and economic cycles.
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