You will never gain success ______ you are fully devoted to your work.
All his free time is ______ by volunteer work, but he feels it meaningful.
The athletes competed ________ each other for gold medals in the Olympic Games.
--Can a plane fly ________ the Atlantic Ocean?--Yes, but it needs to go________ the clouds for hours.
The room ___________ window is open is mine.
Don’t turn on the radio __________ your mother allows you.