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The term Appalachian refers to several different regions associated with the mountain range. Most broadly, it refers to the entire mountain range with its surrounding hills and the dissected plateau region. The term is often used more restrictively to refer to regions in the central and southern Appalachian Mountains, usually including areas in the states of Kentucky, Tennessee, Virginia, Maryland, West Virginia, and North Carolina, as well as sometimes extending as far south as northern Alabama, Georgia and western South Carolina, and as far north as Pennsylvania, southern Ohio and parts of southern upstate New York.
What states comprise of the southern Appalachian mountains?
A: Kentucky, Tennessee, Virginia, Maryland, West Virginia, and North Carolina

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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 4.5–6%. By 2012 available efficiencies exceed 20% and the maximum efficiency of research photovoltaics is over 40%.
What has happened to photovoltaic in the past 20 years?
A: evolved from a pure niche market of small scale applications towards becoming a mainstream electricity source

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Whitehead and Russell had thought originally that Principia Mathematica would take a year to complete; it ended up taking them ten years. To add insult to injury, when it came time for publication, the three-volume work was so massive (more than 2,000 pages) and its audience so narrow (professional mathematicians) that it was initially published at a loss of 600 pounds, 300 of which was paid by Cambridge University Press, 200 by the Royal Society of London, and 50 apiece by Whitehead and Russell themselves. Despite the initial loss, today there is likely no major academic library in the world which does not hold a copy of Principia Mathematica.
Why was there a funding shortfall for the publishing of Princpia Mathematica? 
A: the three-volume work was so massive (more than 2,000 pages) and its audience so narrow (professional mathematicians)

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According to FIG rules, only women compete in rhythmic gymnastics. This is a sport that combines elements of ballet, gymnastics, dance, and apparatus manipulation. The sport involves the performance of five separate routines with the use of five apparatus; ball, ribbon, hoop, clubs, rope—on a floor area, with a much greater emphasis on the aesthetic rather than the acrobatic. There are also group routines consisting of 5 gymnasts and 5 apparatuses of their choice. Rhythmic routines are scored out of a possible 30 points; the score for artistry (choreography and music) is averaged with the score for difficulty of the moves and then added to the score for execution.
What rules state that only women can compete in rhythmic gymastics?
A:
FIG