Answer:
A. Semi periphery.this is the stage
Effective decision-making means comparing the additional
costs of alternatives with the marginal benefits.
To add, <span>a </span>marginal benefit<span> is the additional satisfaction or utility that a
person receives from consuming an additional unit of a good or service.</span> It
is also the topmost amount he is willing to pay to consume that additional
unit of a good or service.
Mentality /Outlook / viewpoint. Here are a few synonyms - they all fit into the space and does not change the original meaning of the sentence.