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
A 35 years old lady presents with post coital bleeding and foul smelling discharge. The most important investigation to arrive at a diagnosis : 
Select and explain. 
A. Endometrial aspiration, B. Dilatation and curettage, C. Endometrial biopsy, D. Cervical biopsy
D: Cervical biopsy
Answer: D: Cervical biopsy 
Explanation: Cervical biopsy