根据以下材料，回答题
Migrant （移民的） Workers
In the past twenty years， there has been an increasing tendency for workers to move from one country to another. While some countries have restricted most __________ （51） to local people，others have attracted and welcomed migrant workers. This is particularly the case in the Middle East， __________ （52） increased oil incomes have enabled many countries to call in outsiders to improve local facilities. Thus the Middle East has attracted oilworkers __________ （53） the U. S. A. and Europe. It has brought in workers from many countries， __________ （54） South Korea and Japan.
In view of the difficult living and worldng __________ （55） in the Middle East， it is not surprising that the pay is high to attract suitable workers. Many engineers and technicians can __________ （56） at least twice as much money in the Middle East as they can in their own country， and this is a major __________ （57）
Sometimes a disadvantage has a compensating （补偿的 ）advantage. For example， the __________ （58）living conditions often lead to increased friendship when workers have to __________ （59） on each other for safety and comfort. In a similar way， many migrant workers can save large sums of money partly because of the __________ （60） of entertainment facilities. The work is often complex and full of problems but this merely __________ （61） greater challenge to engineers who prefer to find solutions to problems rather than do routine work in their home country.
One major problem which __________ （62） migrant workers in the Middle East is that their jobs are temporary ones. They are nearly always on __________ （63） ， so it is not easy for them to plan ahead with great confidence. This is to be __________ （64） since no country welcomes a large number of foreign workers as permanent residents. In any __________ （65）， migrant workers accept this disadvantage， along with others， because of the considerable financial benefits which they receive.
回答（51）题 查看材料

A. cases
B. jobs
C. activities
D. uses