In Response to Some Unexpected Changes in Demand

In response to some unexpected changes in demand:

A) the economy could always adjust its production level if the prices are inflexible.
B) the economy would always produce less than what was expected if the prices of goods and services are inflexible.
C) the economy could always produce at its optimal capacity if the prices of goods and services are inflexible.
D) the economy could always produce at its optimal capacity if the prices of goods and services are fully flexible.