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

The property 'has qualifier' applies to instances of 'Measured Characteristic', and 'PhotonFluxDensity' is a subclass of 'Measured Characteristic'. Which class can appear as the value of 'has qualifier' for instances of 'PhotonFluxDensity'?

A. Measurement
B. Entity
C. Characteristic Qualifier
D. Unit Conversion

Answer: Characteristic Qualifier