Article: The Delhi Metro is a rapid transit system serving New Delhi, Delhi, Gurgaon, Faridabad, Noida, and Ghaziabad in the National Capital Region of India. Delhi Metro is the world's 12th largest metro system in terms of length. Delhi Metro was India's first modern public transportation system, which had revolutionised travel by providing a fast, reliable, safe, and comfortable means of transport. The network consists of six lines with a total length of 189.63 kilometres (117.83 miles) with 142 stations, of which 35 are underground, five are at-grade, and the remainder are elevated. All stations have escalators, elevators, and tactile tiles to guide the visually impaired from station entrances to trains. It has a combination of elevated, at-grade, and underground lines, and uses both broad gauge and standard gauge rolling stock. Four types of rolling stock are used: Mitsubishi-ROTEM Broad gauge, Bombardier MOVIA, Mitsubishi-ROTEM Standard gauge, and CAF Beasain Standard gauge.

Question: What is the name of the world's 12 largest metro system by length?
Ans: The Delhi Metro

Article: In 1880, Bell received the Volta Prize with a purse of 50,000 francs (approximately US$250,000 in today's dollars) for the invention of the telephone from the Academie francaise, representing the French government. Among the luminaries who judged were Victor Hugo and Alexandre Dumas. The Volta Prize was conceived by Napoleon Bonaparte in 1801, and named in honor of Alessandro Volta, with Bell receiving the third grand prize in its history. Since Bell was becoming increasingly affluent, he used his prize money to create endowment funds (the 'Volta Fund') and institutions in and around the United States capital of Washington, D.C.. These included the prestigious 'Volta Laboratory Association' (1880), also known as the Volta Laboratory and as the 'Alexander Graham Bell Laboratory', and which eventually led to the Volta Bureau (1887) as a center for studies on deafness which is still in operation in Georgetown, Washington, D.C. The Volta Laboratory became an experimental facility devoted to scientific discovery, and the very next year it improved Edison's phonograph by substituting wax for tinfoil as the recording medium and incising the recording rather than indenting it, key upgrades that Edison himself later adopted. The laboratory was also the site where he and his associate invented his "proudest achievement", "the photophone", the "optical telephone" which presaged fibre optical telecommunications, while the Volta Bureau would later evolve into the Alexander Graham Bell Association for the Deaf and Hard of Hearing (the AG Bell), a leading center for the research and pedagogy of deafness.

Question: Who first established the Volta Prize?
Ans: Napoleon Bonaparte

Article: Perhaps the biggest sustainability problem in Tucson, with its high desert climate, is potable water supply. The state manages all water in Arizona through its Arizona Department of Water Resources (ADWR). The primary consumer of water is Agriculture (including golf courses), which consumes about 69% of all water. Municipal (which includes residential use) accounts for about 25% of use. Energy consumption and availability is another sustainability issue. However, with over 300 days of full sun a year, Tucson has demonstrated its potential to be an ideal solar energy producer.

Question: How is most of Tucson's water used?
Ans: Agriculture (including golf courses)

Article: Together with caesium and gold (both yellow), and osmium (bluish), copper is one of only four elemental metals with a natural color other than gray or silver. Pure copper is orange-red and acquires a reddish tarnish when exposed to air. The characteristic color of copper results from the electronic transitions between the filled 3d and half-empty 4s atomic shells the energy difference between these shells is such that it corresponds to orange light. The same mechanism accounts for the yellow color of gold and caesium.

Question: How many metals have a natural color that isn't gray?
Ans:
four