What was adam smith's reason for recommending free trade--international trade with no tariffs or other governmental barriers to trade?

What was the main point of helen hunt jackson's book, century of dishonor? a. it showed how unfairly american settlers were treated by the us government. b. it proved that american government was not responsive to the will of the people. c. it made the point that free land was no longer available to new settlers out west. d. it outlined the poor treatment of the native americans by the government.