单项选择题

Zoos have become an important site for the preservation and protection of wildlife resources, (62) those species that are endangered. (63) , many zoos displayed live animals for public entertainment. Presently some zoos have become scientific and educational institutions that have (64) to the understanding and conservation of wild animal populations. Among the (65) facing modern zoos are the cost of upgrading old facilities, the struggle to obtain sufficient operating funds, (66) the need to attract more visitors to new and entertaining exhibits.
Many older zoos in American cities have (67) renovation (翻新) during the last decades of the twentieth century. Among the recent (68) in zoo improvement is the construction of new enclosures that (69) natural habitats (栖息地). The replacement of traditional steel bars and concrete floors (70) appropriately designed surroundings improves visitor appreciation of the animals. Such renovation may (71) stress on animals and allow them to interact with one another more (72) .
Several major zoos (73) captive propagation programs. A captive propagation program includes the breeding of selected zoo or wild animals to obtain offspring, usually for (74) to the wild or for transfer to other zoos. Captive breeding is one method of saving some species (75) extinction.
Zoos have expanded and improved public education programs (76) , with education departments that develop programs (77) to zoo exhibits. Public activities include in-school programs, zoo tours, special events, and websites. The Zoological Society of New York, for example, conducted a major project with a Western African government to (78) an elephant herd as it moved throughout its range.
The importance of zoos will increase (79) natural habitats are diminishing. Through their efforts in (80) of conservation, education, and environmental advocacy, zoos will continue to play a 81 role in wildlife preservation throughout the world.

80（）

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