This task is about writing a correct answer for the reading comprehension task. Based on the information provided in a given passage, you should identify the shortest continuous text span from the passage that serves as an answer to the given question. Avoid answers that are incorrect or provides incomplete justification for the question.
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Question: Passage: Naturally occurring glass, especially the volcanic glass obsidian, has been used by many Stone Age societies across the globe for the production of sharp cutting tools and, due to its limited source areas, was extensively traded. But in general, archaeological evidence suggests that the first true glass was made in coastal north Syria, Mesopotamia or ancient Egypt. The earliest known glass objects, of the mid third millennium BCE, were beads, perhaps initially created as accidental by-products of metal-working (slags) or during the production of faience, a pre-glass vitreous material made by a process similar to glazing. Question: What was obsidian used to make in prehistoric times?

Answer: cutting tools

Question: Passage: The last major building work took place during the reign of King George V when, in 1913, Sir Aston Webb redesigned Blore's 1850 East Front to resemble in part Giacomo Leoni's Lyme Park in Cheshire. This new, refaced principal facade (of Portland stone) was designed to be the backdrop to the Victoria Memorial, a large memorial statue of Queen Victoria, placed outside the main gates. George V, who had succeeded Edward VII in 1910, had a more serious personality than his father; greater emphasis was now placed on official entertaining and royal duties than on lavish parties. He arranged a series of command performances featuring jazz musicians such as the Original Dixieland Jazz Band (1919) the first jazz performance for a head of state, Sidney Bechet, and Louis Armstrong (1932), which earned the palace a nomination in 2009 for a (Kind of) Blue Plaque by the Brecon Jazz Festival as one of the venues making the greatest contribution to jazz music in the United Kingdom. George V's wife Queen Mary was a connoisseur of the arts, and took a keen interest in the Royal Collection of furniture and art, both restoring and adding to it. Queen Mary also had many new fixtures and fittings installed, such as the pair of marble Empire-style chimneypieces by Benjamin Vulliamy, dating from 1810, which the Queen had installed in the ground floor Bow Room, the huge low room at the centre of the garden facade. Queen Mary was also responsible for the decoration of the Blue Drawing Room. This room, 69 feet (21 metres) long, previously known as the South Drawing Room, has a ceiling designed specially by Nash, coffered with huge gilt console brackets. Question: Which king preferred official entertaining and royal duties to lavish parties?

Answer: George V

Question: Passage: Hydrogen poses a number of hazards to human safety, from potential detonations and fires when mixed with air to being an asphyxiant in its pure, oxygen-free form. In addition, liquid hydrogen is a cryogen and presents dangers (such as frostbite) associated with very cold liquids. Hydrogen dissolves in many metals, and, in addition to leaking out, may have adverse effects on them, such as hydrogen embrittlement, leading to cracks and explosions. Hydrogen gas leaking into external air may spontaneously ignite. Moreover, hydrogen fire, while being extremely hot, is almost invisible, and thus can lead to accidental burns. Question: What threats can hydrogen cause to human saftey?

Answer:
potential detonations and fires when mixed with air to being an asphyxiant in its pure, oxygen-free form