Why Would Discovery of a Large,previously Unknown,ongoing Source of Seafloor

Multiple Choice

Why would discovery of a large,previously unknown,ongoing source of seafloor methane probably result in lowering the estimated effects of human civilization on global warming?

A) because it would mean that humans are producing less total methane than had been expected and modeled
B) because methane is an icehouse gas and promotes long-term cooling
C) because it would mean that humans are responsible for a smaller fraction of greenhouse gas production than was previously thought
D) because it would mean that humans are producing less of the other greenhouse gasses than had been expected