Task: Class Relation Understanding (ontology: Sciences/Biology)

Which of the following classes is one valid superclass of 'hygromycin B'?

A. ortho ester
B. ((18)O)water
C. ( Z)-6-benzylidene-3-hydroxymethyl-1,4-dimethyl-3-methylsulfanylpiperazine-2,5-dione
D. ( -)-1-hydroxybybetaochlamic acid

Answer: ortho ester