题目内容：
根据材料，回答问题。Old And Active
It is well-known that life expectancy is longer in Japan than in most other countries. A (51)report also shows that Japan has the longest health expectancy in the world. A healthy long life is the result of the(52)in social environment.
Scientists are trying to work(53)exactly what keeps elderly Japanese people so
healthy, and whether there is a lesson to be(54)from their lifestyles for the rest of us,Should we(55)any changes to our eating habits, for instance, or go jogging each day before breakfast? Is there some secret(56)in the Japanese diet that is particularly (57)to the human body?
Another factor(58)to the rapid population aging in Japan is a decline in birthrate.Although longer life should be celebrated, it is(59)considered a social problem. The number of older people had(60)in the last half century and that has increased pension and medical costs. The country could soon be(61)an economic problem, if there are so many old people to be looked(62), and relatively few younger-people working and paying taxes to support them. (63)the retirement age from 65 to 70 could be one solution to the problem. Work can give the elderly a(64)of responsibility and mission in life. It's important that the elderly play active(65)in the society and live in harmony with all generations.
请在第__(51)__处填上正确答案。 A．late
B．recent
C．contemporary
D．new
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