Task: Inferred Class Relation Reasoning (ontology: Sciences/Biology)

After reasoning, which of the following classes is one valid superclass of 'cytochrome-b5 reductase activity, acting on NAD(P)H'?

A. appressorium maturation
B. obsolete 9-phenanthrol glycosyltransferase activity
C. oxidoreductase activity, acting on NAD(P)H
D. RNA polymerase complex

Answer: oxidoreductase activity, acting on NAD(P)H