Which of the following items could serve as a secondary source for a historian studying early chinese history?

a. a bronze plow discovered in the ruins of an ancient chinese city
b. a chart created in ancient china to track a city's growing population
c. an essay about china's first emperor written by a university professor
d. an announcement written for an early chinese emperor to deliver to his subjects

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.  

congress also has implied powers, which derive from the necessary and proper clause of the constitution and permit congress "to make all laws which shall be necessary and proper for carrying into execution the foregoing powers, and all other powers vested by this constitution in the government of the united states.