The problem: Answer a question about this article:
Polarization is predictable from an antenna's geometry, although in some cases it is not at all obvious (such as for the quad antenna). An antenna's linear polarization is generally along the direction (as viewed from the receiving location) of the antenna's currents when such a direction can be defined. For instance, a vertical whip antenna or Wi-Fi antenna vertically oriented will transmit and receive in the vertical polarization. Antennas with horizontal elements, such as most rooftop TV antennas in the United States, are horizontally polarized (broadcast TV in the U.S. usually uses horizontal polarization). Even when the antenna system has a vertical orientation, such as an array of horizontal dipole antennas, the polarization is in the horizontal direction corresponding to the current flow. The polarization of a commercial antenna is an essential specification.
The polarization of what antenna is essential specification?
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The answer: commercial antenna

The problem: Answer a question about this article:
Portugal (Portuguese: [putua]), officially the Portuguese Republic (Portuguese: Republica Portuguesa), is a country on the Iberian Peninsula, in Southwestern Europe. It is the westernmost country of mainland Europe, being bordered by the Atlantic Ocean to the west and south and by Spain to the north and east. The PortugalSpain border is 1,214 km (754 mi) long and considered the longest uninterrupted border within the European Union. The republic also includes the Atlantic archipelagos of the Azores and Madeira, both autonomous regions with their own regional governments.
What is the longest uninterrupted border within the European Union?
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The answer: PortugalSpain

The problem: Answer a question about this article:
This was the first season where the contestants were permitted to perform in the final rounds songs they wrote themselves. In the Top 8, Sam Woolf received the fewest votes, but he was saved from elimination by the judges. The 500th episode of the series was the Top 3 performance night.
At what point in season 13 did American Idol air its 500th show?
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The answer: Top 3 performance night

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Perspectives on emotions from evolutionary theory were initiated in the late 19th century with Charles Darwin's book The Expression of the Emotions in Man and Animals. Darwin argued that emotions actually served a purpose for humans, in communication and also in aiding their survival. Darwin, therefore, argued that emotions evolved via natural selection and therefore have universal cross-cultural counterparts. Darwin also detailed the virtues of experiencing emotions and the parallel experiences that occur in animals. This led the way for animal research on emotions and the eventual determination of the neural underpinnings of emotion.
In what century did Darwin write?
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The answer:
19th