Hypothesis (Part I): At a once-daily dose that is sufficiently safe and well tolerated in HCV-infected participants, elbasvir administered for 5 consecutive days has superior antiviral activity in GT1 HCV-infected participants compared to placebo, as measured by change from baseline in plasma HCV ribonucleic acid (RNA; log 10 copies/mL) at Day 5, 24-hour postdose timepoint. (a true mean viral RNA reduction of at least 3 log10 is anticipated).