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

Which of the following definitions best describes 'progoitrin'?

A. The stereoisomer of xi-progoitrin that has S at the carbon bearing the allylic hydroxy group.
B. The stereoisomer of xi-the concept that has R at the carbon bearing the allylic hydroxy group.
C. A beta-D-glucosyl-(1<->1')-N-acylsphinganine in which the acyl group specified is hexacosanoyl.
D. An epoxy steroid that is 3beta-hydroxypregnenolone 3-beta-D-glucoside in which the hydrogens at the 16alpha and 17alpha positions have been replaced by the oxygen of the epoxide ring.

Answer: The stereoisomer of xi-the concept that has R at the carbon bearing the allylic hydroxy group.