According to Smith the correct answer is C. gain the greatest possible profit.
Adam Smith says when an individual invests their capital in domestic industry he is searching for the greatest value this capital can return for him, but by doing it the society will also benefit.
A. ask the government to control commerce this option is wrong as he thinks the market must be free and open, thus the government responsibilities should be limited to matters related to education, defence or infrastructure.
B. nurture trade with foreign is wrong because he arguments for local investment and even to lay tax on foreign products for internal economic grown and to encourage domestic economy.
D. promote the public good of their country, this option is not correct because the promotion of the public good is done by daily choices not by investing capital in industry.