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

Which of the following definitions best describes 'aquatic estuarine layer'?

A. A layer of liquid that is part of an estuary.
B. The surface layer of a volume of water.
C. A roughly planar, pelagic region characterised by equal salinity.
D. A roughly planar, pelagic region characterised by equal water density.

Answer: A layer of liquid that is part of an estuary.