This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General obstetrics, Subject name: Gynaecology & Obstetrics
Periconceptional use of the following agent leads to reduced incidence of neural tube defects? 
Select and explain. 
A. Folic acid, B. Iron, C. Calcium, D. Vitamin A
A: Folic acid
Answer: A: Folic acid 
Explanation: Folic acid supplementation (4mg a day) staing 4 weeks prior to conception up to 12 weeks of pregnancy is advised.This can reduce the incidence of neural tube defects.Reference: DC Dutta&;s Textbook of Obstetrics, 8th edition, page no:472