When a Firm Is Making a Profit-Maximising Production Decision, Which

When a firm is making a profit-maximising production decision, which one of the Ten Lessons of Economics is likely to be most important to their decision?

A) governments can sometimes improve market outcomes
B) the cost of something is what you give up to get it
C) a country's standard of living depends on its ability to produce goods and services
D) prices rise when the government prints too much money