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
Spontaneous abortion in 1st trimester is caused by:a) Trisomy 21b) Monosomy c) Traumad) Rh-incompatibility 
Select and explain. 
A. ab, B. bc, C. acd, D. abc
D: abc
Answer: D: abc 
Explanation: Common causes of abortion