Which of the following best describes a carbon sink?

A carbon sink is best described as an area that absorbs more carbon dioxide from the atmosphere than it releases. This characteristic is crucial for mitigating climate change, as carbon sinks help to reduce the overall concentration of carbon dioxide, a greenhouse gas, in the atmosphere. Examples of carbon sinks include forests, oceans, and soil, which play vital roles in sequestering carbon.

In contrast, the other options do not accurately describe a carbon sink. A source of carbon emissions would indicate a net release of carbon dioxide into the atmosphere, which is the opposite of a carbon sink. A natural process that produces carbon dioxide describes emissions rather than absorption, highlighting activities such as respiration or combustion. Lastly, a process that accelerates climate change would also relate to the increase of greenhouse gases rather than their absorption. Hence, option B captures the essence of what a carbon sink is and its importance in the context of environmental science and climate mitigation efforts.