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数据结构包括三方面的内容：数据的逻辑结构、数据的存储结构和数据的【3】。

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Zoos have become an important site for the preservation and protection of wildlife resources, (61) those species that are endangered. (62) , many zoos displayed live animals for public entertainment. Presently some zoos have become scientific and educational (63) that have contributed to the understanding and conservation of wild animal populations. (64) the challenges facing modern zoos are the cost of upgrading old facilities, the struggle to obtain 65 operating funds, and the need to attract more visitors to new and entertaining exhibits. Many (66) zoos in American cities have undergone renovation (翻新) during the last decades of the twentieth century. Among the recent trends in zoo (67) is the construction of new enclosures that resemble natural habitats (栖息地). The replacement of traditional steel bars and concrete floors (68) appropriately designed surroundings improves visitor appreciation of the animals. Such renovations may (69) stress on animals and allow them to interact with one another more naturally. Several major zoos conduct captive propagation programs. A captive propagation program includes the breeding of (70) zoo or wild animals to obtain offspring, usually for release to (71) or for transfer to other zoos. Captive breeding is one method of 72 some species from extinction. Zoos have expanded and improved public education programs also, with education departments that develop programs (73) zoo exhibits. Public activities include in-school programs, zoos tours, special events, and websites. The Zoological Society of New York, for example, conducted a major project with a Western African government to monitor an elephant herd (74) it moved throughout its range. The importance of zoos will increase as natural habitats are diminishing. Through will their efforts (75) conservation, education, and environmental advocacy, zoos continue to play a critical role in wildlife preservation throughout the world.

A. selected
B. sustained
C. promising
D. surviving

数据库恢复通常基于数据备份和【15】。

膳食中维生素B的来源：（）

A动物肝、肾、牛奶
B粮谷类
C绿叶类
D酱菜类
E干豆、花生

基因工程是指在（）水平上，采用与（）设计十分类似的方法，按照人类的需要进行设计，然后按设计方案创建出具有某种新的性状的生物新品系，并能使之稳定地遗传给后代。