please explain

A client has asked you to review the mining and resource market for a possible investment in Eco Grande, a large copper producing company. Recent market reports indicate an unanticipated sharp decline in copper inventories. Other things remaining constant, what effect will this have on copper prices, if the supply of copper continues to fall? a) Prices will fall until new copper reserves are found. b) Prices will rise due to the supply shortage. c) Prices will remain unchanged because copper does not represent a major manufacturing component and thus there is little demand for copper anyway. d) Prices will fall due to the increase in demand for copper