People should open the window in the morning to make air ______ in order to keep the indoor air fresh.
Her family _____ much larger than mine four years ago. Her family _____ dancing and singing when I came in last night.
A knife and a fork _____ on the table. A knife and fork _____ on the table.
Many a professor _____ looking forward to visiting Germany now. Many scientists _____ studied animals and plants in the last two years.
Either you or he _____ interested in playing chess. _____ you or he fond of music at present?
He is one of the boys who _____ here on time. He is the only one of the boys who _____ here on time.