Task: Property Constraint Reasoning (ontology: Earth_Environment/EnvironmentOntology)

The property 'causal relation between processes' applies to instances of 'occurrent', and 'process boundary' is a subclass of 'occurrent'. Which class can appear as the value of 'causal relation between processes' for instances of 'process boundary'?

A. occurrent
B. donor
C. obsolete unpasteurized caprine milk
D. obsolete cervid milk

Answer: occurrent