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.

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

Classical India refers to the period when much of the Indian subcontinent was reunited under the Gupta Empire (c. 320550 CE). This period has been called the Golden Age of India and was marked by extensive achievements in science, technology, engineering, art, dialectic, literature, logic, mathematics, astronomy, religion, and philosophy that crystallized the elements of what is generally known as Hindu culture. The Hindu-Arabic numerals, a positional numeral system, originated in India and was later transmitted to the West through the Arabs. Early Hindu numerals had only nine symbols, until 600 to 800 CE, when a symbol for zero was developed for the numeral system. The peace and prosperity created under leadership of Guptas enabled the pursuit of scientific and artistic endeavors in India.
By what is India under the Gupta Empire referered?

In cities other than Rome, the name cardinal began to be applied to certain church men as a mark of honour. The earliest example of this occurs in a letter sent by Pope Zacharias in 747 to Pippin III (the Short), ruler of the Franks, in which Zacharias applied the title to the priests of Paris to distinguish them from country clergy. This meaning of the word spread rapidly, and from the 9th century various episcopal cities had a special class among the clergy known as cardinals. The use of the title was reserved for the cardinals of Rome in 1567 by Pius V.
What term was given to certain church men of honor?