This task is about reading the given passage and construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) its answer is a continuous text span from the paragraph. Avoid creating questions that (i) can be answered correctly without actually understanding the paragraph and (ii) uses same words or phrases given in the passage.
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Question: 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.

Answer: In what year was a large scale solar distillation project constructed in Las Salinas?

Question: The last opus number that Chopin himself used was 65, allocated to the Cello Sonata in G minor. He expressed a deathbed wish that all his unpublished manuscripts be destroyed. At the request of the composer's mother and sisters, however, his musical executor Julian Fontana selected 23 unpublished piano pieces and grouped them into eight further opus numbers (Opp. 6673), published in 1855. In 1857, 17 Polish songs that Chopin wrote at various stages of his life were collected and published as Op. 74, though their order within the opus did not reflect the order of composition.

Answer: What was the last number Chopin gave to an opus?

Question: Although Classical music in the 2000s has lost most of its tradition for musical improvisation, from the Baroque era to the Romantic era, there are examples of performers who could improvise in the style of their era. In the Baroque era, organ performers would improvise preludes, keyboard performers playing harpsichord would improvise chords from the figured bass symbols beneath the bass notes of the basso continuo part and both vocal and instrumental performers would improvise musical ornaments. J.S. Bach was particularly noted for his complex improvisations. During the Classical era, the composer-performer Mozart was noted for his ability to improvise melodies in different styles. During the Classical era, some virtuoso soloists would improvise the cadenza sections of a concerto. During the Romantic era, Beethoven would improvise at the piano. For more information, see Improvisation.

Answer:
Classical music in the 2000s has lost most of its tradition for musical what?