The total combined income of 48 countries in Africa is only a little more than _____ of Belgium.
Before the tourists set off, they spent much time setting a limit __________ the expenses of the trip.
There is a limit __________ people's life, but no limit __________ the knowledge.
Unfortunately, the research was limited __________ increasing economic profits,__________ protecting the environment.
They are trying to find a new way to __________ the spread of AIDS.
They will have you __________ if you don't pay taxes, because it is everyone's duty to pay taxes.