Problem: Frederic Chopin:

From September 1823 to 1826 Chopin attended the Warsaw Lyceum, where he received organ lessons from the Czech musician Wilhelm Wurfel during his first year. In the autumn of 1826 he began a three-year course under the Silesian composer Jozef Elsner at the Warsaw Conservatory, studying music theory, figured bass and composition.[n 3] Throughout this period he continued to compose and to give recitals in concerts and salons in Warsaw. He was engaged by the inventors of a mechanical organ, the "eolomelodicon", and on this instrument in May 1825 he performed his own improvisation and part of a concerto by Moscheles. The success of this concert led to an invitation to give a similar recital on the instrument before Tsar Alexander I, who was visiting Warsaw; the Tsar presented him with a diamond ring. At a subsequent eolomelodicon concert on 10 June 1825, Chopin performed his Rondo Op. 1. This was the first of his works to be commercially published and earned him his first mention in the foreign press, when the Leipzig Allgemeine Musikalische Zeitung praised his "wealth of musical ideas".

What instrument did Chopin play in front of Tsar Alexander I?
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A: eolomelodicon

Problem: Russian Soviet Federative Socialist Republic:

Internationally, in 1920, the RSFSR was recognized as an independent state only by Estonia, Finland, Latvia and Lithuania in the Treaty of Tartu and by the short-lived Irish Republic.

What treaty resulted in the nonrecognition of the RSFSR by Latvia and other states?
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A: unanswerable

Problem: Russian Soviet Federative Socialist Republic:

On June 12, 1990, the Congress of People's Deputies of the Republic adopted the Declaration of State Sovereignty of the Russian SFSR, which was the beginning of the "War of Laws", pitting the Soviet Union against the Russian Federation and other constituent republics.

What body rejected the Declaration of State Sovereignty of the Russian SFSR?
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A: unanswerable

Problem: Solar energy:

Solar distillation can be used to make saline or brackish water potable. The first recorded instance of this was by 16th-century Arab alchemists. A large-scale solar distillation project was first constructed in 1872 in the Chilean mining town of Las Salinas. The plant, which had solar collection area of 4,700 m2 (51,000 sq ft), could produce up to 22,700 L (5,000 imp gal; 6,000 US gal) per day and operate for 40 years. Individual still designs include single-slope, double-slope (or greenhouse type), vertical, conical, inverted absorber, multi-wick, and multiple effect. These stills can operate in passive, active, or hybrid modes. Double-slope stills are the most economical for decentralized domestic purposes, while active multiple effect units are more suitable for large-scale applications.

What is used to make saline or brackish water drinkable?
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A:
Solar distillation