Q: What is a question about this article? If the question is unanswerable, say "unanswerable".
Since the beginning of the study of electricity non conductive materials like glass, porcelain, paper and mica have been used as insulators. These materials some decades later were also well-suited for further use as the dielectric for the first capacitors. Paper capacitors made by sandwiching a strip of impregnated paper between strips of metal, and rolling the result into a cylinder were commonly used in the late 19century; their manufacture started in 1876, and they were used from the early 20th century as decoupling capacitors in telecommunications (telephony).
Besides porcelain, paper and mica, what other conductive material was used as an insulator?
A: unanswerable

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In the late 14th century, the Songhai gradually gained independence from the Mali Empire and expanded, ultimately subsuming the entire eastern portion of the Mali Empire. The Songhai Empire's eventual collapse was largely the result of a Moroccan invasion in 1591, under the command of Judar Pasha. The fall of the Songhai Empire marked the end of the region's role as a trading crossroads. Following the establishment of sea routes by the European powers, the trans-Saharan trade routes lost significance.
Who gained independence in the 1400s?
A: unanswerable

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Grove Street Cemetery, a National Historic Landmark which lies adjacent to Yale's campus, contains the graves of Roger Sherman, Eli Whitney, Noah Webster, Josiah Willard Gibbs, Charles Goodyear and Walter Camp, among other notable burials. The cemetery is known for its grand Egyptian Revival gateway. The Union League Club of New Haven building, located on Chapel Street, is notable for not only being a historic Beaux-Arts building, but also is built on the site where Roger Sherman's home once stood; George Washington is known to have stayed at the Sherman residence while President in 1789 (one of three times Washington visited New Haven throughout his lifetime).
Roger Sherman once lived in Chapel Street, in modern day what is the name building that sit in its' place?
A: Union League Club

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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 five-layer PCB can be fabricated how?
A:
unanswerable