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

The property 'has substance added' applies to instances of 'material entity', and 'root' is a subclass of 'material entity'. Which class can appear as the value of 'has substance added' for instances of 'root'?

A. famine
B. plant structure development stage
C. acceptor
D. material entity

Answer: material entity