<qa>  What is a non childbearing potential?- Is of non childbearing potential or agrees to avoid becoming pregnant or impregnating a partner beginning at least 2 weeks prior to administration of the initial dose of study drug and for 14 days after the last dose of study drug if not taking RBV, or for 6 months after the last dose of study drug if taking RBV or longer if dictated by local regulations. If not abstinent from heterosexual activity, participants in Part A must use 2 acceptable forms of barrier contraception whereas participants in Parts B and C must use 2 acceptable forms of contraception which may include oral contraceptives 