Extract the answer to the question from the following context. Question: The melting point of __is 1855 °C . Context: Glass has the ability to refract, reflect, and transmit light following geometrical optics, without scattering it. It is used in the manufacture of lenses and windows. Common glass has a refraction index around 1.5. This may be modified by adding low-density materials such as boron, which lowers the index of refraction (see crown glass), or increased (to as much as 1.8) with high-density materials such as (classically) lead oxide (see flint glass and lead glass), or in modern uses, less toxic oxides of zirconium, titanium, or barium. These high-index glasses (inaccurately known as "crystal" when used in glass vessels) cause more chromatic dispersion of light, and are prized for their diamond-like optical properties.
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Answer: zirconium


Extract the answer to the question from the following context. Question: While Oklahoma is ranked high for much of it's energy production, when do it's rankings begin to collapse? Context: Oklahoma is the nation's third-largest producer of natural gas, fifth-largest producer of crude oil, and has the second-greatest number of active drilling rigs, and ranks fifth in crude oil reserves. While the state ranked eighth for installed wind energy capacity in 2011, it is at the bottom of states in usage of renewable energy, with 94 percent of its electricity being generated by non-renewable sources in 2009, including 25 percent from coal and 46 percent from natural gas. Oklahoma has no nuclear power. Ranking 13th for total energy consumption per capita in 2009, Oklahoma's energy costs were 8th lowest in the nation.
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Answer: in usage of renewable energy


Extract the answer to the question from the following context. Question: What did Antarctica and Australia do during the Eocene period? Context: During the Eocene (56 million years ago - 33.9 million years ago), the continents continued to drift toward their present positions. At the beginning of the period, Australia and Antarctica remained connected, and warm equatorial currents mixed with colder Antarctic waters, distributing the heat around the world and keeping global temperatures high. But when Australia split from the southern continent around 45 Ma, the warm equatorial currents were deflected away from Antarctica, and an isolated cold water channel developed between the two continents. The Antarctic region cooled down, and the ocean surrounding Antarctica began to freeze, sending cold water and ice floes north, reinforcing the cooling. The present pattern of ice ages began about 40 million years ago.[citation needed]
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Answer:
drift toward their present positions