This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
The property of proteins to absorb ultraviolet rays of light is due to 
Select and explain. 
A. Peptide bond, B. Imino group, C. Di Sulphide bond, D. Aromatic amino acid
D: Aromatic amino acid
Answer: D: Aromatic amino acid 
Explanation: Aromatic side chains (aromatic amino acids) are responsible for the UV light absorption of most proteins.