单选题：根据材料回答题：Migrant workersIn the past twenty years, there has

根据材料回答题：
Migrant workers
In the past twenty years, there has been an increasing tendency for workers to move from onecountry to another.__________(51) some newly independent countries have understandably restrictedmost jobs to local people, others have attracted and welcomed migrant workers. This is particularlthe case in the Middle East,__________(52) increased oil incomes have enabled many countries to____________(53) outsiders to improve local facilities.__________(54) the Middle East has attracted oil-workers from the U. S. A. and Europe. It has brought in construction workers and technicians frommany countries,__________(55) South Korea and Japan.
In view of the difficult living and working conditions in the Middle East, it is not__________(56) that the pay is high to attract suitable workers. Many engineers and technicians can earn at least__________(57) money in the Middle East as they can in their own country, and this is a major attrae~tion. An aliied benefit is the low taxation or complete lack of it. This increases the.net amount of payreceived by visiting workers and is very popular with them.
Sometimes a disadvantage has a compensating advantage.__________(58) , the difficult living condi~tions often lead to increased friendship when workers have to depend on each other__________(59) safe-ty and comfort.__________(60), many migrant workers can save large sumsof money partly__________(61)the lack of entertainment facilities. The work is often complex and full of problems but this merelypresents greater challenge to engineers who prefer to find solutions__________(62) problems ratherthan do routine work in their home country.
One major problem which__________(63) migrant workers in the Middle East is that their jobs are temporary ones. They are nearly always on contract, so it is not easy for them to plan ahead with greatconfidence. This is to be expected since no country, welcomes a large number of foreign workers as per-manent residents.__________(64), migrant workers accept thin disadvantage, along with others, because of the__________(65) financial benefits which they receive.
__________ A．As
B．Since
C．While
D．Although