Which action would most likely increase the amount of carbon in the environment?

Cutting down of most of the trees in the forest to make furniture.

Deforestation is the phenomena of clearance, clearing or removal of forests to make the land available for human use like agriculture, industrialization and urban development. Carbon from air is taken up by trees in order to prepare their food by the process of photosynthesis and releases oxygen. Cutting down of trees will increase the level of carbon dioxide in the environment.

there are so many examples for that in different areas, like biology experiment carried out in our lab recently.

here's one link:

allowed for the prediction of the properties of missing elements.