Which Actor Plays the Most Active and Direct Role in Sustainability

Which actor plays the most active and direct role in sustainability transitions and why?

A) Niche actors; they act as a protective space which promotes experimentation and development of new innovations
B) National government; it efficiently organizes key resource flow to establish new markets for innovation
C) Regime actors; they work to change existing institutions from the inside out by supporting powerful coalitions
D) Intermediaries; they are designed to foster innovation, encourage connections between entrepreneurs and policy makers, and scale-up new technologies