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: Skin
A patient has syphilis since 2 year. CSF examination was done & treatment staed. Which of the following test is most useful in monitoring treatment 
Select and explain. 
A. TPI, B. VDRL, C. FTA, D. Dark ground microscopy
B: VDRL
Answer: B: VDRL 
Explanation: B i.e. VDRL