Question

clear cell carcinoma of the vagina is thought to have been caused by:
exposure in utero to diethylstilbestrol (des)
unopposed progesterone stimulation
human papillomavirus (hpv)
herpesvirus
high level of estrogen

Explanation:

Clear cell carcinoma of the vagina is known to be associated with in - utero exposure to Diethylstilbestrol (DES). Unopposed progesterone stimulation, HPV, Herpesvirus, and high estrogen levels are not the established causes for this specific type of vaginal carcinoma.

Answer:

A. Exposure in utero to Diethylstilbestrol (DES)