Economists use changes in gdp to measure

Economists use changes in GDP to measure the state of a country's economy.  The gross domestic product, also known as GDP, is a tool that economists around the world use to measure how the economy of a specific country is doing. They use this tool, because it represents the value in american dollars, of all the services and goods that a country produced during a specific amount of time. This number gives an estimation on how big or small the country's economy is.

the correct answer is “opportunity cost”. opportunity cost is what a company misses out because it decided in one option over another one. in this case, the company decided to invest in building a factory so it gave up another possible benefit or profit in order to achieve success with the factory.  

trade-off is not the correct answer since it is a situation in which you accept losing something in return for benefits in other areas.

and finally, consequence is a general term used to accept what it comes when you make a decision. it can be a positive or negative consequence depending if the decision you took was the correct one.