In 1975, a Pocket Calculator Cost More Than $50; in 1990

In 1975, a pocket calculator cost more than $50; in 1990, a calculator of the same quality cost less than $10. Which of the following explanations is most consistent with these facts?

A) As the population grew, fewer expensive calculators were needed, causing prices to fall.
B) Intense competition in the calculator industry caused the supply curve for calculators to shift to the left, depressing the price.
C) An improvement in technology caused the supply of calculators to increase, depressing their price.
D) An increase in the demand for calculators led to the price drop.