The passage suggests that an assumption underlying non-economist social scientists dismal of economics as dismal is that
A． positive-sum outcomes cannot, by the definition of the power model, exist
B． all social sciences founded on pragmatism instead of idealism are dismal
C． zero-sum interactions models are inherently optimistic in their view of the future
D． scarcity does not necessarily exist as a controlling factor in social systems
E． economics is anti-utopian by nature, proposing a more realistic view of the future