Problem: Renewable energy commercialization:

Hydroelectricity is the term referring to electricity generated by hydropower; the production of electrical power through the use of the gravitational force of falling or flowing water. It is the most widely used form of renewable energy, accounting for 16 percent of global electricity generation 3,427 terawatt-hours of electricity production in 2010, and is expected to increase about 3.1% each year for the next 25 years. Hydroelectric plants have the advantage of being long-lived and many existing plants have operated for more than 100 years.

What is the least widely used form of renewable energy?
---
A: unanswerable

Problem: Detroit remains one of the most racially segregated cities in the United States. From the 1940s to the 1970s a second wave of Blacks moved to Detroit to escape Jim Crow laws in the south and find jobs. However, they soon found themselves excluded from white areas of the citythrough violence, laws, and economic discrimination (e.g., redlining). White residents attacked black homes: breaking windows, starting fires, and exploding bombs. The pattern of segregation was later magnified by white migration to the suburbs. One of the implications of racial segregation, which correlates with class segregation, may be overall worse health for some populations.
What exacerbated segregation in Detroit?
---
Answer: white migration to the suburbs

Q: What is a question about this article? If the question is unanswerable, say "unanswerable".
It was only in the 1980s that digital telephony transmission networks became possible, such as with ISDN networks, assuring a minimum bit rate (usually 128 kilobits/s) for compressed video and audio transmission. During this time, there was also research into other forms of digital video and audio communication. Many of these technologies, such as the Media space, are not as widely used today as videoconferencing but were still an important area of research. The first dedicated systems started to appear in the market as ISDN networks were expanding throughout the world. One of the first commercial videoconferencing systems sold to companies came from PictureTel Corp., which had an Initial Public Offering in November, 1984.
What is the minimum bit rate for compressed video and audio transmission?
A: 128 kilobits/s

Context and question: In February 2016, it was confirmed by BBC Worldwide that Keeping Up Appearances is the corporation's most exported television programme, being sold nearly 1000 times to overseas broadcasters.
How many sales of Keeping Up Appearances have been made to non-British buyers?
Answer: nearly 1000

Question: The actual substance of English law was formally "received" into the United States in several ways. First, all U.S. states except Louisiana have enacted "reception statutes" which generally state that the common law of England (particularly judge-made law) is the law of the state to the extent that it is not repugnant to domestic law or indigenous conditions. Some reception statutes impose a specific cutoff date for reception, such as the date of a colony's founding, while others are deliberately vague. Thus, contemporary U.S. courts often cite pre-Revolution cases when discussing the evolution of an ancient judge-made common law principle into its modern form, such as the heightened duty of care traditionally imposed upon common carriers.
Is there an answer to this question: What are reception statutes?

Answer: the common law of England (particularly judge-made law) is the law of the state

Q: What is a question about this article? If the question is unanswerable, say "unanswerable".
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.
Name a reason to take a database backward in time?
A:
database is found corrupted