Problem: Electric motor:

In 1827, Hungarian physicist Ányos Jedlik started experimenting with electromagnetic coils. After Jedlik solved the technical problems of the continuous rotation with the invention of the commutator, he called his early devices "electromagnetic self-rotors". Although they were used only for instructional purposes, in 1828 Jedlik demonstrated the first device to contain the three main components of practical DC motors: the stator, rotor and commutator. The device employed no permanent magnets, as the magnetic fields of both the stationary and revolving components were produced solely by the currents flowing through their windings.

What discovery solved the problem of continuous rotation?
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A: commutator


Problem: Leucothea was daughter of Orchamus and sister of Clytia. She fell in love with Apollo who disguised himself as Leucothea's mother to gain entrance to her chambers. Clytia, jealous of her sister because she wanted Apollo for herself, told Orchamus the truth, betraying her sister's trust and confidence in her. Enraged, Orchamus ordered Leucothea to be buried alive. Apollo refused to forgive Clytia for betraying his beloved, and a grieving Clytia wilted and slowly died. Apollo changed her into an incense plant, either heliotrope or sunflower, which follows the sun every day.
Who was Leucothea's mother?
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Answer: Orchamus


Q: What is a question about this article? If the question is unanswerable, say "unanswerable".
On September 30, 1987, Foster filed an application with the United States Patent and Trademark Office to patent his invented sport. The patent application covered the rules of the game, specifically detailing the goalposts and rebound netting and their impact on gameplay. Foster's application was granted on March 27, 1990. The patent expired on September 30, 2007.
With whom did Foster file his patent?
A: the United States Patent and Trademark Office


Context and question: The last opus number that Chopin himself used was 65, allocated to the Cello Sonata in G minor. He expressed a deathbed wish that all his unpublished manuscripts be destroyed. At the request of the composer's mother and sisters, however, his musical executor Julian Fontana selected 23 unpublished piano pieces and grouped them into eight further opus numbers (Opp. 66–73), published in 1855. In 1857, 17 Polish songs that Chopin wrote at various stages of his life were collected and published as Op. 74, though their order within the opus did not reflect the order of composition.
What is the last opus number that Chopin used?
Answer: 65


Question: In 2012, New York City had the lowest overall crime rate and the second lowest murder rate among the largest U.S. cities, having become significantly safer after a spike in crime in the 1970s through 1990s. Violent crime in New York City decreased more than 75% from 1993 to 2005, and continued decreasing during periods when the nation as a whole saw increases. By 2002, New York City's crime rate was similar to that of Provo, Utah, and was ranked 197th in crime among the 216 U.S. cities with populations greater than 100,000. In 2005 the homicide rate was at its lowest level since 1966, and in 2007 the city recorded fewer than 500 homicides for the first time ever since crime statistics were first published in 1963. In the first six months of 2010, 95.1% of all murder victims and 95.9% of all shooting victims in New York City were black or Hispanic; additionally, 90.2 percent of those arrested for murder and 96.7 percent of those arrested for shooting someone were black or Hispanic. New York experienced a record low of 328 homicides in 2014 and has a far lower murder rate than other major American cities.
Is there an answer to this question: What percentage decrease in violent crime did the city see between 1993 and 2005?

Answer: 75%


Question: Biodiversity provides critical support for drug discovery and the availability of medicinal resources. A significant proportion of drugs are derived, directly or indirectly, from biological sources: at least 50% of the pharmaceutical compounds on the US market are derived from plants, animals, and micro-organisms, while about 80% of the world population depends on medicines from nature (used in either modern or traditional medical practice) for primary healthcare. Only a tiny fraction of wild species has been investigated for medical potential. Biodiversity has been critical to advances throughout the field of bionics. Evidence from market analysis and biodiversity science indicates that the decline in output from the pharmaceutical sector since the mid-1980s can be attributed to a move away from natural product exploration ("bioprospecting") in favor of genomics and synthetic chemistry, indeed claims about the value of undiscovered pharmaceuticals may not provide enough incentive for companies in free markets to search for them because of the high cost of development; meanwhile, natural products have a long history of supporting significant economic and health innovation. Marine ecosystems are particularly important, although inappropriate bioprospecting can increase biodiversity loss, as well as violating the laws of the communities and states from which the resources are taken.
Is there an answer to this question: What ecosystems are particularly natural?

Answer:
unanswerable