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

Which of the following classes is one valid superclass of 'agricultural wastewater treatment plant'?

A. wastewater treatment plant
B. 1st arch mesenchyme from neural crest
C. 1st arch mesenchyme from head mesenchyme
D. 17beta-hydroxy steroid

Answer: wastewater treatment plant