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

Which of the following classes does 'Arctic front' belong to as one valid explicit type? Context: A polar front between the deep, cold Arctic air and the shallower, warmer polar air of northern latitudes on Earth.

A. frontal surface of a weather front
B. marine cline
C. polar front
D. occluded front

Answer: polar front