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: Gynaecology & Obstetrics
In case of Twining true statement is: 
Select and explain. 
A. After embryonic disc fusion, conjoint twin is formed., B. Incidence of monozygotic twin varies with race, C. Incidence of dizygotic twin is constant, D. The frequency of monozygosity and dizygosity is same.
A: After embryonic disc fusion, conjoint twin is formed.
Answer: A: After embryonic disc fusion, conjoint twin is formed. 
Explanation: After embryonic disc fusion, conjoint twin is formed.