According to Warren Buffett,which of the Following Is the Most

According to Warren Buffett,which of the following is the most important lesson on growth and profitability?

A) Investors should have invested in the car industry in the early 20^th century.
B) Investors should have invested in the aircraft manufacturing industry in the early 20^th century.
C) One should look to invest in economically important sectors of the economy that have room for many firms.
D) Understanding a firm's competitive advantage is more important than understanding the firm's growth rate or impact on society.