In which market would the price be least likely to be "sticky"?

Economists have found that as a nation's per capita real Gross Domestic Product (GDP) increases

A) the rate of population growth declines. B) the rate of population growth experiences dramatic increases. C) there is no effect on population growth. D) the rate of population growth increases at the same rate as economic growth.

Which market is most likely to witness such actions and reactions as frequent new-product introductions, free samples, and aggressive advertising campaigns?

a. Oligopoly b. Perfect competition c. Monopoly d. Monopolistic competition