Please excuse me _______ your letter by mistake.
In the competition to be held, a gold medal, together with a certain sum of money, _____ the champion.
You can only be sure of _____ you have at present; you cannot be sure of something _____ you might get in the future.
The traditional view is _____ we sleep because our brain is “programmed” to make us do so.
We arranged to meet at the cinema at 7:30, but he failed to ______.
Miss Green contributed fifty dollars, but she wished she could contribute _____.