—Can I pay the bill by check?--- Sorry, sir. But it is the management rules of our hotel that payment ____ be made in cash.
The professor devoted all his life __________ the treatment of AIDS.
He was __________ down for several days after he heard the bad news.
They all looked down upon him. He was __________ a singer.
In the experiment we kept a watchful eye __________ the development and recorded every detail.
My interest in collecting stamps __________ my childhood.