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

Which of the following definitions best describes 'anaerobic sediment'?

A. Sediment hosting and characterised by active sulphate reducing microbial communities.
B. Sediment hosting and characterised by active carbon dioxide reducing microbial communities.
C. Sediment characterised by an average particle diameter below 1 micrometer.
D. Sediment characterised by the absence of oxygen.

Answer: Sediment characterised by the absence of oxygen.