Answer:
The correct answer is: The law of comparative advantage.
Step-by-step explanation:
Comparative advantage refers to the situation when an individual, a firm, or a nation can produce a good or service at a comparatively lower opportunity cost.
With the opening up of trade the nation or individual will produce and trade the good it has a comparative advantage in or the good it specializes in producing.
It will export this good to others and import the goods it has a higher opportunity cost in producing. In this way, both the nations or individuals will be able to consume beyond their production possibilities curves.