Input: Article: In the last two decades, photovoltaics (PV), also known as solar PV, has evolved from a pure niche market of small scale applications towards becoming a mainstream electricity source. A solar cell is a device that converts light directly into electricity using the photoelectric effect. The first solar cell was constructed by Charles Fritts in the 1880s. In 1931 a German engineer, Dr Bruno Lange, developed a photo cell using silver selenide in place of copper oxide. Although the prototype selenium cells converted less than 1% of incident light into electricity, both Ernst Werner von Siemens and James Clerk Maxwell recognized the importance of this discovery. Following the work of Russell Ohl in the 1940s, researchers Gerald Pearson, Calvin Fuller and Daryl Chapin created the crystalline silicon solar cell in 1954. These early solar cells cost 286 USD/watt and reached efficiencies of 4.56%. By 2012 available efficiencies exceed 20% and the maximum efficiency of research photovoltaics is over 40%.

Now answer this question: What has happened to photovoltaic in the past 20 years?

Output: evolved from a pure niche market of small scale applications towards becoming a mainstream electricity source

Article: Prior to the Reformation, the Polish nobility were mostly either Roman Catholic or Orthodox with a small group of Muslims. Many families, however, soon adopted the Reformed faiths. After the Counter-Reformation, when the Roman Catholic Church regained power in Poland, the nobility became almost exclusively Catholic, despite the fact that Roman Catholicism was not the majority religion in Commonwealth (the Catholic and Orthodox churches each accounted for some 40% of all citizens population, with the remaining 20% being Jews or members of Protestant denominations). In the 18th century, many followers of Jacob Frank joined the ranks of Jewish-descended Polish gentry. Although Jewish religion wasn't usually a pretext to block or deprive of noble status, some laws favoured religious conversion from Judaism to Christianity (see: Neophyte) by rewarding it with ennoblement.

Question: What two religions were most common?
Ans: Roman Catholic or Orthodox

Here is a question about this article: Garze Tibetan Autonomous Prefecture and Ngawa Tibetan and Qiang Autonomous Prefecture in western Sichuan are populated by Tibetans and Qiang people. Tibetans speak the Khams and Amdo Tibetan, which are Tibetic languages, as well as various Qiangic languages. The Qiang speak Qiangic languages and often Tibetic languages as well. The Yi people of Liangshan Yi Autonomous Prefecture in southern Sichuan speak the Nuosu language, which is one of the Lolo-Burmese languages; Yi is written using the Yi script, a syllabary standardized in 1974. The Southwest University for Nationalities has one of China's most prominent Tibetology departments, and the Southwest Minorities Publishing House prints literature in minority languages. In the minority inhabited regions of Sichuan, there is bi-lingual signage and public school instruction in non-Mandarin minority languages.
What is the answer to this question: What are the largest minorities of western Sichuan?
****
So... Tibetans and Qiang

The problem: Answer a question about this article:
The first commercial LEDs were commonly used as replacements for incandescent and neon indicator lamps, and in seven-segment displays, first in expensive equipment such as laboratory and electronics test equipment, then later in such appliances as TVs, radios, telephones, calculators, as well as watches (see list of signal uses). Until 1968, visible and infrared LEDs were extremely costly, in the order of US$200 per unit, and so had little practical use. The Monsanto Company was the first organization to mass-produce visible LEDs, using gallium arsenide phosphide (GaAsP) in 1968 to produce red LEDs suitable for indicators. Hewlett Packard (HP) introduced LEDs in 1968, initially using GaAsP supplied by Monsanto. These red LEDs were bright enough only for use as indicators, as the light output was not enough to illuminate an area. Readouts in calculators were so small that plastic lenses were built over each digit to make them legible. Later, other colors became widely available and appeared in appliances and equipment. In the 1970s commercially successful LED devices at less than five cents each were produced by Fairchild Optoelectronics. These devices employed compound semiconductor chips fabricated with the planar process invented by Dr. Jean Hoerni at Fairchild Semiconductor. The combination of planar processing for chip fabrication and innovative packaging methods enabled the team at Fairchild led by optoelectronics pioneer Thomas Brandt to achieve the needed cost reductions. These methods continue to be used by LED producers.
What was the first commercial uses of LEDs?
****
The answer: replacements for incandescent and neon indicator lamps

Problem: Please answer a question about the following article about Saint Barth%C3%A9lemy:
Among the notable structures in the town are the three forts built by the Swedes for defense purposes. One of these forts, known as Fort Oscar (formerly Gustav Adolph), which overlooks the sea is located on the far side of La Pointe. However, the ruins have been replaced by a modern military building which now houses the local gendarmerie. The other fort known as Fort Karl now presents a very few ruins. The third fort built by the Swedes is the Fort Gustav, which is also seen in ruins strewn around the weather station and the Light House. The fort built in 1787 over a hill slope has ruins of ramparts, guardhouse, munitions depot, wood-burning oven and so forth.
Most of the Forts in St. Barts are now all what?
A: ruins

Question: Read this and answer the question

There are many styles of mandolin, but four are common, the Neapolitan or round-backed mandolin, the carved-top mandolin and the flat-backed mandolin. The round-back has a deep bottom, constructed of strips of wood, glued together into a bowl. The carved-top or arch-top mandolin has a much shallower, arched back, and an arched topboth carved out of wood. The flat-backed mandolin uses thin sheets of wood for the body, braced on the inside for strength in a similar manner to a guitar. Each style of instrument has its own sound quality and is associated with particular forms of music. Neapolitan mandolins feature prominently in European classical music and traditional music. Carved-top instruments are common in American folk music and bluegrass music. Flat-backed instruments are commonly used in Irish, British and Brazilian folk music. Some modern Brazilian instruments feature an extra fifth course tuned a fifth lower than the standard fourth course.

Which mandolin is commin in American Folk music and blue grass music?
Answer:
Carved-top instruments