Ans. is 'c' i.e., Transformation zone Site of origin of cervical carcinomao Squamocolumnar junction (SCJ) is the meeting point of columnar epithelium, that lines the endocervical canal, with squamous epithelium that lines the ectocervix. This SCJ is a dynamic point. It moves up and down in relation to different phases of life, e.g. puberty, pregnancy and menopause. Following image shows shows the cyclical changes in squamocolumnar junction:A) Before puberty, the ectocervix is covered with squamous epitheliumB) Hightened estrogenic activity exposes the columnar epithelium onto the ectocervixC) Replacement of columnar epithelium by squamous epithelium to form TZ. New squamocolumnar junction is situated at or slightly outside the external os during reproductive periodD) Indrawing of the squamocolumnar junction and the TZ well into the cervical canal following menopause.o The metaplasia extends from the original SCJ (now squamosquamous) outside to the newly developed (physiologically active) SCJ (now squamocolumnar) inside. This area is defined as transformation zone (TZ).o The process of carcinogenesis starts at this 'transformation zone' (TZ). The zone is not static but in a dynamic state.o Two mechanisms are involved in the process of replacement of endocervical columnar epithelium by squamous epithelium:# By squamous metaplasia of the subcolumnar reserve cells.# Squamous epidermidization by ingrowth of the squamous epithelium of the ectocervix under the columnar epithelium.o Initially, the squamous cells are immature but ultimately become mature and indistinguishable to the adjacent squamous epithelium.o This metaplastic process is very active at the time of menarche and during and after first pregnancy. These periods are of high estrogenic phase which lowers the vaginal pH. The acid pH probably is an important trigger for the metaplastic process.o Thesemetaplastic cells have got the potentiality to undergo atypical transformation by trauma or infectiono The prolonged effect of carcinogens can produce continuous changes in the immature cells which may lead to malignancy. Early age sexual activity and multiple sexual partners are the most consistent risk factors. HPV infection is transmitted through sexual activity.o Microtrauma (sexual intercourse) causes viral entry to the epithelium (basal or parabasal cells) of the transformation zone adjacent to the SCJ.o HPV- DNA positivity is strongly related with the number of sexual partners. Women with multiple partners have high HPV DNA positivity rate (60%) compared to women with single partner (21%).o The important factors in the genesis of cervieal cancer are:i) Infection with high-risk HPVii) Multiple types of HPViii) Persistence of infectioniv) Age >30 yearsv) Smokingvi) Compromised host immunodefense