Please answer this: Question: "Backup files are tied to?" Context: "Sometimes it is desired to bring a database back to a previous state (for many reasons, e.g., cases when the database is found corrupted due to a software error, or if it has been updated with erroneous data). To achieve this a backup operation is done occasionally or continuously, where each desired database state (i.e., the values of its data and their embedding in database's data structures) is kept within dedicated backup files (many techniques exist to do this effectively). When this state is needed, i.e., when it is decided by a database administrator to bring the database back to this state (e.g., by specifying this state by a desired point in time when the database was in this state), these files are utilized to restore that state." Answer:
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Answer: time

Please answer this: Question: "The influx of immigrants was explained by?" Context: "By 1990, the Census Bureau included more than a dozen ethnic/racial categories on the census, reflecting not only changing social ideas about ethnicity, but the wide variety of immigrants who had come to reside in the United States due to changing historical forces and new immigration laws in the 1960s. With a changing society, more citizens have begun to press for acknowledging multiracial ancestry. The Census Bureau changed its data collection by allowing people to self-identify as more than one ethnicity. Some ethnic groups are concerned about the potential political and economic effects, as federal assistance to historically underserved groups has depended on Census data. According to the Census Bureau, as of 2002, over 75% of all African Americans had multiracial ancestries." Answer:
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Answer: changing historical forces and new immigration laws

Please answer this: Question: "The attempt to get Whooping cranes to migrate back to the U.S. is an example of what type of ecological program?" Context: "It has been possible to teach a migration route to a flock of birds, for example in re-introduction schemes. After a trial with Canada geese Branta canadensis, microlight aircraft were used in the US to teach safe migration routes to reintroduced whooping cranes Grus americana." Answer:
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Answer:
re-introduction schemes