Bill has a good mood today, he looks (more happy / happier / more happily) than he was yesterday.
Bill has a good mood today, he looks (more happy / happier / more happily) than he was yesterday.
"Happier" là so sánh hơn của "happy" → bỏ "y" thêm "ier".
Dịch: Hôm nay tâm trạng của Bill rất tốt, cậu ấy trông vui vẻ hơn hôm qua.