Due to the unreasonable individual income ______, the gap between the rich and poor has become an outstanding issue.
The house built of stone lasts longer than ____ built of wood.
It is ______ that terrorism is a great threat to world peace.
With the worldwide oil crisis, the price of oil has been raised ______ 15%.
Part of the work is to be finished today and ______ by this weekend.
It is no longer a problem _______ the poor children in this district can go to school.