Problem: Renewable energy commercialization:

Hydropower is produced in 150 countries, with the Asia-Pacific region generating 32 percent of global hydropower in 2010. China is the largest hydroelectricity producer, with 721 terawatt-hours of production in 2010, representing around 17 percent of domestic electricity use. There are now three hydroelectricity plants larger than 10 GW: the Three Gorges Dam in China, Itaipu Dam across the Brazil/Paraguay border, and Guri Dam in Venezuela. The cost of hydroelectricity is low, making it a competitive source of renewable electricity. The average cost of electricity from a hydro plant larger than 10 megawatts is 3 to 5 U.S. cents per kilowatt-hour.

How many hydroelectricity plants are larger than 10 GW?
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A: three

Problem: Printed circuit board:

The hole walls for boards with two or more layers can be made conductive and then electroplated with copper to form plated-through holes. These holes electrically connect the conducting layers of the PCB. For multi-layer boards, those with three layers or more, drilling typically produces a smear of the high temperature decomposition products of bonding agent in the laminate system. Before the holes can be plated through, this smear must be removed by a chemical de-smear process, or by plasma-etch. The de-smear process ensures that a good connection is made to the copper layers when the hole is plated through. On high reliability boards a process called etch-back is performed chemically with a potassium permanganate based etchant or plasma. The etch-back removes resin and the glass fibers so that the copper layers extend into the hole and as the hole is plated become integral with the deposited copper.

The back-etch removes what?
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A: unanswerable

Problem: Late Middle Ages:

Hunyadi succeeded during the Siege of Belgrade in 1456 against the Ottomans, the biggest victory against that empire in decades. This battle became a real Crusade against the Muslims, as the peasants were motivated by the Franciscan monk Saint John of Capistrano, who came from Italy predicating Holy War. The effect that it created in that time was one of the main factors that helped in achieving the victory. However the premature death of the Hungarian Lord left Pannonia defenseless and in chaos. In an extremely unusual event for the Middle Ages, Hunyadi's son, Matthias, was elected as King of Hungary by the nobility. For the first time, a member of an aristocratic family (and not from a royal family) was crowned.

Who did the Hungarian nobility elect as King of Hungary?
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A: Matthias

Problem: Hard rock:

Hard rock is a form of loud, aggressive rock music. The electric guitar is often emphasised, used with distortion and other effects, both as a rhythm instrument using repetitive riffs with a varying degree of complexity, and as a solo lead instrument. Drumming characteristically focuses on driving rhythms, strong bass drum and a backbeat on snare, sometimes using cymbals for emphasis. The bass guitar works in conjunction with the drums, occasionally playing riffs, but usually providing a backing for the rhythm and lead guitars. Vocals are often growling, raspy, or involve screaming or wailing, sometimes in a high range, or even falsetto voice.

What instrument is often used in soft rock music?
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A:
unanswerable