In today's economy, we have not only rich and poor people but also rich and poor countries. This is because we do not exist in a __________, a world society consisting of only sovereign, self-contained territories. Instead, we are part of a __________, a global market organized by a capitalist economy.

 a. global city; nation-state system

 b. nation-state system; world system

 c. world system; nation-state system

 d. world system; global city