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
The essential investigation to be included In follow-up of hydatidiform mole is : 
Select and explain. 
A. Ultrasound abdomen, B. Chest X ray, C. Serum levels of HCG, D. Serum levels of TSH
C: Serum levels of HCG
Answer: C: Serum levels of HCG 
Explanation: Serum levels of HCG