<prompt> Protective factor for ovarian cancer:NulliparityBilateral TubectomyDysgenetic gonadsWoker of asbestos industry  <response>: Ans is b, i.e. Bilateral tubectomyRef: William gynae 3ed, p736Tubal ligation and Hysterectomy are each associated with a substantial reduction in risk. Theoretically, any gynecological procedure that precludes intants from reaching the ovaries via as caesarian from the lower genital tract might plausibly exert a similar protective effect. - Ref: Williams Gynae 3rded, p736 