(c) Economic system
The Bretton Woods system was based on an economic system — specifically fixed exchange rates, aimed at ensuring economic stability and full employment in the industrial world.
Source: Post-war Settlement and the Bretton Woods Institutions, Chapter 3
The passage clearly states that the Bretton Woods system was built on fixed exchange rates and economic goals (full employment, price stability). The IMF and World Bank — its key institutions — are economic bodies. Options (a), (b), and (d) have no support in the text.