Which of these is also known as ''marsh gas''?

A marsh is a wetland dominated by plants that have no persistent woody stems. It is a mixture of methane, hydrogen sulfide, carbon dioxide (CO2) and traces of phosphine (PH3) produced naturally. The surface of marshes is initially porous vegetation that forms a soil crust preventing oxygen from reaching the organic material trapped below. This is the condition that allows anaerobic (without oxygen) digestion and fermentation of any plant, which produces methane. The trapped methane is able to escape through any of these three main path ways, viz., ebullition, plant-mediated transportation and diffusion. This methane is the primary gas that makes up the product colloquially known as ''marsh gas''.

The methane is produced by the decomposition of organic matter in low oxygen conditions. Normally, 20.9% of the gas is in the atmosphere. In water, oxygen levels are much lower approximately 7 parts per million (ppm) in good quality of water. The diffusion can be accelerated at night when heat is emitted from the water surface. Ebullition or bubbling is a type of oneday transport of gases to the water column and then to the atmosphere. Much of the methane produced is derived from either an acetate (salt of acetic acid) cleavage or by the hydrogen reduction of CO2. Methane can also be produced by the methanogens (microorganisms), that are found in marsh environments. The bubbles of methane created by methanogens, that are present in the marsh commonly known as marsh gas.