Article: A mandolin (Italian: mandolino pronounced [mandolino]; literally "small mandola") is a musical instrument in the lute family and is usually plucked with a plectrum or "pick". It commonly has four courses of doubled metal strings tuned in unison (8 strings), although five (10 strings) and six (12 strings) course versions also exist. The courses are normally tuned in a succession of perfect fifths. It is the soprano member of a family that includes the mandola, octave mandolin, mandocello and mandobass.

Question: How is the mandolin usually played?
Ans: usually plucked with a plectrum or "pick"

Article: The dates are generalizations, since the periods and eras overlap and the categories are somewhat arbitrary, to the point that some authorities reverse terminologies and refer to a common practice "era" comprising baroque, classical, and romantic "periods". For example, the use of counterpoint and fugue, which is considered characteristic of the Baroque era (or period), was continued by Haydn, who is classified as typical of the Classical era. Beethoven, who is often described as a founder of the Romantic era, and Brahms, who is classified as Romantic, also used counterpoint and fugue, but other characteristics of their music define their era.

Question: Some authorities reverse terminologies to refer to the common practice period as a what?
Ans: era

Article: DC commutating electric motors, if fitted with laminated pole pieces, become universal motors because they can also operate on AC; reversing the current in both stator and rotor does not reverse the motor. But the now-standard AC distribution frequencies of 50 and 60 Hz caused difficulties with inductive reactance and eddy current losses. Many railways chose low AC frequencies to overcome these problems. They must be converted from utility power by motor-generators or static inverters at the feeding substations or generated at dedicated traction powerstations.

Question: How can low frequencies be obtained?
Ans: converted from utility power

Article: Based on experience with German strategic bombing during World War I against the United Kingdom, the British government estimated after the war that 50 casualties with about one third killed would result for every tonne of bombs dropped on London. The estimate of tonnes of bombs an enemy could drop per day grew as aircraft technology advanced, from 75 in 1922, to 150 in 1934, to 644 in 1937. That year the Committee on Imperial Defence estimated that an attack of 60 days would result in 600,000 dead and 1,200,000 wounded. News reports of the Spanish Civil War, such as the bombing of Barcelona, supported the 50-casualties-per-tonne estimate. By 1938 experts generally expected that Germany would attempt to drop as much as 3,500 tonnes in the first 24 hours of war and average 700 tonnes a day for several weeks. In addition to high explosive and incendiary bombs the enemy would possibly use poison gas and even bacteriological warfare, all with a high degree of accuracy. In 1939 military theorist Basil Liddell-Hart predicted that 250,000 deaths and injuries in Britain could occur in the first week of war.

Question: What committee estimated that 60 days of attacks would result in 600,000 deaths?
Ans:
Imperial Defence