**Core Concept**
Early age of sexual initiation is associated with an increased risk of certain types of cancer due to the prolonged exposure to oncogenic human papillomavirus (HPV) infections. This risk is particularly pronounced for cervical cancer, as HPV is a well-established cause of cervical neoplasia.

**Why the Correct Answer is Right**
The correct answer is A. Carcinoma cervix because HPV, particularly high-risk types such as HPV-16 and HPV-18, is a primary cause of cervical cancer. Early initiation of sexual activity increases the likelihood of acquiring HPV, which can lead to persistent infection and subsequent carcinogenesis. The cervix is the most common site for HPV-related cancers, and early age of sexual debut is a significant risk factor for the development of cervical cancer.

**Why Each Wrong Option is Incorrect**
**Option B:** Carcinoma vulva is less commonly associated with HPV and more often linked to other risk factors such as smoking and immunosuppression.
**Option C:** Carcinoma vagina is rare in the general population and more often seen in the context of other risk factors such as radiation exposure or human immunodeficiency virus (HIV) infection.
**Option D:** Carcinoma ovary is not directly associated with HPV and has a more complex etiology involving genetic, hormonal, and environmental factors.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that HPV vaccination has been shown to reduce the incidence of cervical cancer and other HPV-related diseases, making it a critical tool in cancer prevention. The vaccine's effectiveness is highest when administered before sexual debut, underscoring the importance of early vaccination.

**✓ Correct Answer: A. Carcinoma cervix**