Task: Class Definition Understanding (ontology: Earth_Environment/EnvironmentOntology)

Which of the following definitions best describes 'methane ice'?

A. the concept is a light, black residue, consisting of carbon and any remaining ash, obtained by removing water and other volatile constituents from animal and vegetation substances. the concept is usually produced by slow pyrolysis, the heating of wood or other substances in the absence of oxygen.
B. Kerogen which has a hydrogen to carbon ratio less than 0.5 and primarily composed of polycyclic aromatic hydrocarbons.
C. Ice which is primarily composed of carbon dioxide.
D. Ice which is primarily composed of methane.

Answer: Ice which is primarily composed of methane.