Problem: Railway electrification system:

A railway electrification system supplies electric power to railway trains and trams without an on-board prime mover or local fuel supply. Electrification has many advantages but requires significant capital expenditure. Selection of an electrification system is based on economics of energy supply, maintenance, and capital cost compared to the revenue obtained for freight and passenger traffic. Different systems are used for urban and intercity areas; some electric locomotives can switch to different supply voltages to allow flexibility in operation.

What system supplies nuclear power to railway trains?
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A: unanswerable

Problem: United States dollar:

Early releases of the Washington coin included error coins shipped primarily from the Philadelphia mint to Florida and Tennessee banks. Highly sought after by collectors, and trading for as much as $850 each within a week of discovery, the error coins were identified by the absence of the edge impressions "E PLURIBUS UNUM IN GOD WE TRUST 2007 P". The mint of origin is generally accepted to be mostly Philadelphia, although identifying the source mint is impossible without opening a mint pack also containing marked units. Edge lettering is minted in both orientations with respect to "heads", some amateur collectors were initially duped into buying "upside down lettering error" coins. Some cynics also erroneously point out that the Federal Reserve makes more profit from dollar bills than dollar coins because they wear out in a few years, whereas coins are more permanent. The fallacy of this argument arises because new notes printed to replace worn out notes, which have been withdrawn from circulation, bring in no net revenue to the government to offset the costs of printing new notes and destroying the old ones. As most vending machines are incapable of making change in banknotes, they commonly accept only $1 bills, though a few will give change in dollar coins.

What do collectors commonly only accept?
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A: unanswerable

Problem: Guam:

Wildfires plague the forested areas of Guam every dry season despite the island's humid climate. Most fires are man-caused with 80% resulting from arson. Poachers often start fires to attract deer to the new growth. Invasive grass species that rely on fire as part of their natural life cycle grow in many regularly burned areas. Grasslands and "barrens" have replaced previously forested areas leading to greater soil erosion. During the rainy season sediment is carried by the heavy rains into the Fena Lake Reservoir and Ugum River, leading to water quality problems for southern Guam. Eroded silt also destroys the marine life in reefs around the island. Soil stabilization efforts by volunteers and forestry workers (planting trees) have had little success in preserving natural habitats.

What are 20% of fires resulting from?
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A: unanswerable

Problem: Late Middle Ages:

Changes also took place within the recruitment and composition of armies. The use of the national or feudal levy was gradually replaced by paid troops of domestic retinues or foreign mercenaries. The practice was associated with Edward III of England and the condottieri of the Italian city-states. All over Europe, Swiss soldiers were in particularly high demand. At the same time, the period also saw the emergence of the first permanent armies. It was in Valois France, under the heavy demands of the Hundred Years' War, that the armed forces gradually assumed a permanent nature.

Which English king is associated with the use of mercenaries in the 14th century?
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A:
Edward III