In His Book, the Wealth of Nations, Adam Smith Made

In his book, The Wealth of Nations, Adam Smith made the following observation?

A) ​There is no such thing as a free lunch.
B) ​People buy more when prices are low than when prices are high.
C) ​No matter how much people make, they tend to spend more than they make.
D) ​People tend to pursue their own personal interest and that an invisible hand (the market) guides their self-interest, increasing social welfare and economic well being.