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

The property 'has target unit' applies to instances of 'Unit Conversion', and 'MicrosecondToSecond' is a subclass of 'Unit Conversion'. Which class can appear as the value of 'has target unit' for instances of 'MicrosecondToSecond'?

A. Characteristic
B. Unit
C. Index
D. Entity

Answer: Unit