题目内容：
根据以下材料，回答题Why India Needs Its Dying Vultures
The vultures (秃鹰) in question may look ugly and threatening, but the sudden sharp decline in three species of India's vultures is producing alarm rather than celebration, and it presents the world with a new kind of environmental problem. The dramatic__________(51) in vulture numbers is causing widespread disruption to people living in the__________(52) areas as the birds. It is also causing serious public health problems __________(53) the Indian sub-continent.
While their reputation and appearance may be unpleasant to many Indians, vultures have__________(54)played a very important role in keeping towns and villages all over India __________(55) It is because they feed on dead cows. In India, cows are sacred animals and are__________ (56) left in the open when they die in their thousands upon thousands every year.
The disappearance of the vultures has __________(57) an explosion in the numbers of wild dogs feeding on the remains of these__________ (58) animals. There are fears that rabies (狂犬症) may increase as a result. And this terrifying disease may ultimately (最终) affect humans in the region, __________ (59) ild dogs are its main carriers. Rabies could also spread to other animal species, __________(60) an even greater problem in the future.
The need for action is __________ (61), so an emergency project has been launched to find a solution to this serious vulture problem. Scientists are trying to__________ (62) the disease causing the birds' deaths and, if possible, develop a cure.
Large-scale vulture__________(63) were first noticed at the end of the 1980s in India. A population survey at that time showed that the three species of vultures had declined__________ (64)over 90 per cent. All three species are now listed as "critically endangered". As most vultures lay only single eggs and__________ (65) about five years to reach maturity, reversing their population decline will be a long and difficult exercise.
回答(51)题 A．increase
B．threat
C．risk
D．decline
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