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

Which of the following definitions best describes '2-methylbutanal'?

A. A methylbutanal that is butanal substituted by a methyl group at position 3. It occurs as a volatile constituent in olives.
B. A 2-methylbutanal that has S configuration.
C. A member of the class of propanals that is propanal substituted by a methyl group at position 2.
D. A methylbutanal in which the methyl substituent is at position 2.

Answer: A methylbutanal in which the methyl substituent is at position 2.