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

After reasoning, which of the following classes is one valid superclass of 'thetin-homocysteine S-methyltransferase activity'?

A. catalytic activity
B. positive regulation of methane biosynthetic process from methanethiol
C. response to antineoplastic agent
D. positive regulation of cuticle pigmentation

Answer: catalytic activity