This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology, Subject name: Biochemistry
Chemically, oestrogens are characterised by 
Select and explain. 
A. Absence of O2 at D-17, B. Aromatic character at D-ring, C. Absence to methyl group at C-10, D. A 21-carbon steroid skeleton
C: Absence to methyl group at C-10
Answer: C: Absence to methyl group at C-10 
Explanation: One hydroxyl group attached to the D ring