Protective factor for ovarian cancer:
High-Yield Explanation
Ans is b, i.e. Bilateral tubectomyRef: William gynae 3/ed, p736"Tubal 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 3rd/ed, p736