Which of the Following Would Best Benefit the Development of Niche

Which of the following would best benefit the development of niche marketing?

A) A decline in the cost of advertising on radio and newspapers enabling firms to more efficiently reach a wide audience.
B) A growing acceptance of free trade agreements such as NAFTA.
C) A Supreme Court ruling that limits the market share individual firms in a market are allowed to serve.
D) A manufacturing improvement enabling firms to more efficiently design and produce specialized products for small groups of consumers.