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
Concentration of DNA is measured by- 
Select and explain. 
A. Absorption at 260 nm, B. D-oxyribose estimation, C. Infrared examination, D. Ultrasound examination
A: Absorption at 260 nm
Answer: A: Absorption at 260 nm 
Explanation: Concentration (and quality) of nucleotides and nucleic acid (DNA/RNA) is measured in terms of "absorbance at 260 nm" with a Ultraviolet (UV) spectrophotometer.