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: Physiology
Which of the following method is sensitive for easy assessment of hormonal activity? 
Select and explain. 
A. Chromatography, B. ELISA, C. Radio-immunoassay, D. Cytochemistry assay
B: ELISA
Answer: B: ELISA 
Explanation: It is cost effective and does not employ radio active isotopes. It is the basic principle for measuring the concentration of a hormone. Ref: guyton and hall textbook of medical physiology 12 edition page number: 535,536,537