What Basic Argument Did Adam Smith Make in His Book,The

What basic argument did Adam Smith make in his book,The Wealth of Nations?

A) Someone will be more successful in business if he or she is a leader and true entrepreneur.
B) Socialism is the best economic system.
C) National wealth was created fastest by the mercantile system.
D) Government should not interfere in the economy,but should let businesses function without regulation or restriction.
E) The government should own the means of production.