Here is so difficult a problem_______none of us can solve.
We __________ him __________ his winning the first prize.
John is ill and has been __________ by Tom in our team in tomorrow's football match.
She concentrated her energies __________ her test.
My deskmate and Tom are similar __________ each other __________ character.
The company,__________ in 2003, is one of the most famous compa-nies.