An ________ boy, Li Wen, works hard and gets good grades in his final exam.
eighteen-year-olds
eighteen-year-old
eighteen years old
The singing group will have two performances ______ October.
The supermarket is open ______ midnight.
She didn’t go to work ______ that morning. She slept ______ noon.
He was ill _____ a week, and _______ the week he ate almost nothing .
Days are longer ______ summer than ___________ winter.