What is meant by the phrase "free trade"?
A. That companies are expected to make less profit
B. That there are no shipping costs within those countries
C. That international business is not limited by tariffs or quotas
D. That products traded between those countries are at no charge

C. International business shouldn't be limited by high tariffs or quotas. Free trade means that business should take its course without the hindrance of quotas, tariffs, or other restrictions.

porter is writing economic history because he is focusing on the cost of developing vaccines.

this question makes no sense dude