What Reason Is Cited by the Authors for the Difficulty

What reason is cited by the authors for the difficulty with receiving approval for sustainability as a strategy?

A) Sustainability is not a classic strategy in the mold of quality, cost leadership, or flexibility.
B) Sustainability is too easily achieved and therefore does not provide a competitive advantage in the market.
C) In general, directors often need to see a demonstrable return on investment to justify the costs.
D) Sustainability is an inherently high-risk strategy and most boards are risk-averse.