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
Which is the most common agent responsible for Ca cervix? 
Select and explain. 
A. HPV 16, B. HPV 18, C. HPV 31, D. HPV 33
A: HPV 16
Answer: A: HPV 16 
Explanation: HPV 16 is responsible for about 50% of cervical cancer, and is the most common agent responsible for carcinoma cervix. Other HPV strains associated with cervical cancer are HPV 18, 31 and 45. Ref: Textbook of gynecology by D C Dutta 4th edition Page 316, 322; ALCAMOS'S fundamentals of microbiology By Jeffrey C Pommerville page 829; Johns Hopkins Manual of Gynecology and Obstetrics, The, 3rd Edition, chapter 41.