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
Most frequent chromosomal abnormality found in those with heart defect 
Select and explain. 
A. Trisomy 13, B. Trisomy 21, C. Trisomy 18, D. Monosomy X
B: Trisomy 21
Answer: B: Trisomy 21 
Explanation: Trisomy 21 >> Trisomy 18 >> 22q Microdeletion >> Trisomy 13 >> monosomy X.
This is order of occurrence of heart defect most commonly and frequently.