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Multi-layer printed circuit boards have trace layers inside the board. This is achieved by laminating a stack of materials in a press by applying pressure and heat for a period of time. This results in an inseparable one piece product. For example, a four-layer PCB can be fabricated by starting from a two-sided copper-clad laminate, etch the circuitry on both sides, then laminate to the top and bottom pre-preg and copper foil. It is then drilled, plated, and etched again to get traces on top and bottom layers.
A silver-clad laminate can be found in what kind of circuit board?
A: unanswerable

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Eritrea can be split into three ecoregions. To the east of the highlands are the hot, arid coastal plains stretching down to the southeast of the country. The cooler, more fertile highlands, reaching up to 3000m has a different habitat. Habitats here vary from the sub-tropical rainforest at Filfil Solomona to the precipitous cliffs and canyons of the southern highlands. The Afar Triangle or Danakil Depression of Eritrea is the probable location of a triple junction where three tectonic plates are pulling away from one another.The highest point of the country, Emba Soira, is located in the center of Eritrea, at 3,018 meters (9,902 ft) above sea level.
How high is Emba Soira?
A: 3,018 meters (9,902 ft) above sea level

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As a more urban culture developed, academies provided a means of transmission for speculative and philosophical literature in early civilizations, resulting in the prevalence of literature in Ancient China, Ancient India, Persia and Ancient Greece and Rome. Many works of earlier periods, even in narrative form, had a covert moral or didactic purpose, such as the Sanskrit Panchatantra or the Metamorphoses of Ovid. Drama and satire also developed as urban culture provided a larger public audience, and later readership, for literary production. Lyric poetry (as opposed to epic poetry) was often the speciality of courts and aristocratic circles, particularly in East Asia where songs were collected by the Chinese aristocracy as poems, the most notable being the Shijing or Book of Songs. Over a long period, the poetry of popular pre-literate balladry and song interpenetrated and eventually influenced poetry in the literary medium.
From what settings did lyric poetry derive?
A: courts and aristocratic circles

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On 16 March 2011, the freighter MS Oliva ran aground on Nightingale Island, spilling tons of heavy fuel oil into the ocean, leaving an oil slick threatening the island's population of rockhopper penguins. Nightingale Island has no fresh water, so the penguins were transported to Tristan da Cunha for cleaning.
What was spilled into rockhopper penguins on March 16, 2011?
A:
unanswerable