The carbon offset market:

The carbon offset market allows companies and individuals to purchase carbon credits to compensate for their emissions.

Why C (voluntary and regulated aspects) is correct:

Regulated markets: Compliance-based (e.g., EU Emissions Trading System, California Cap-and-Trade Program).

Voluntary markets: Used by companies seeking to offset their carbon footprints (e.g., via Verra, Gold Standard projects).

Why not A or B?

A (Very transparent) is incorrect—voluntary carbon markets often lack transparency and face greenwashing risks.

B (Rigorous scientific process) is partly true but varies widely between high-quality and low-quality offsets.