What Does It Mean to Offset Your Greenhouse Gas Emissions

What does it mean to offset your greenhouse gas emissions?

A) Removing as many tons of greenhouse gases from the atmosphere as you emit into the atmosphere.
B) Ensuring that the greenhouse gases that you would cause to be emitted are captured and stored rather than emitted into the atmosphere.
C) Ensuring that for every ton of greenhouse gases you emit, a ton of greenhouse gases is either removed from the atmosphere or prevented from being emitted in the first place.
D) Compensating others for the harm caused by the greenhouse gases that you emit, even if you cannot be sure that the specific people you are compensating are the people harmed by your emissions in particular.