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

Which of the following classes is one valid superclass of 'concentration of thallium in lake water'?

A. 3-oxo-Delta(4) steroid
B. concentration of
C. 1st arch mesenchyme from neural crest
D. 1st arch mandibular mesenchyme from neural crest

Answer: concentration of