Problem: Light-emitting diode:

Machine vision systems often require bright and homogeneous illumination, so features of interest are easier to process. LEDs are often used for this purpose, and this is likely to remain one of their major uses until the price drops low enough to make signaling and illumination uses more widespread. Barcode scanners are the most common example of machine vision, and many low cost products use red LEDs instead of lasers. Optical computer mice are an example of LEDs in machine vision, as it is used to provide an even light source on the surface for the miniature camera within the mouse. LEDs constitute a nearly ideal light source for machine vision systems for several reasons:

What is the most uncommon example of a machine vision system?
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A: unanswerable

Problem: Paris was in its artistic prime in the 19th century and early 20th century, when it had a colony of artists established in the city and in art schools associated with some of the finest painters of the times: Manet, Monet, Berthe Morisot, Gauguin, Renoir and others. The French Revolution and political and social change in France had a profound influence on art in the capital. Paris was central to the development of Romanticism in art, with painters such as Gericault. Impressionism, Art Nouveau, Symbolism, Fauvism Cubism and Art Deco movements all evolved in Paris. In the late 19th century, many artists in the French provinces and worldwide flocked to Paris to exhibit their works in the numerous salons and expositions and make a name for themselves. Artists such as Pablo Picasso, Henri Matisse, Vincent van Gogh, Paul Cezanne, Jean Metzinger, Albert Gleizes, Henri Rousseau, Marc Chagall, Amedeo Modigliani and many others became associated with Paris. Picasso, living in Montmartre, painted his famous La Famille de Saltimbanques and Les Demoiselles d'Avignon between 1905 and 1907. Montmartre and Montparnasse became centres for artistic production.
In what town did Picasso live?
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Answer: Montmartre

Q: What is a question about this article? If the question is unanswerable, say "unanswerable".
Chinese men entered the United States as laborers, primarily on the West Coast and in western territories. Following the Reconstruction era, as blacks set up independent farms, white planters imported Chinese laborers to satisfy their need for labor. In 1882, the Chinese Exclusion Act was passed, and Chinese workers who chose to stay in the U.S. were unable to have their wives join them. In the South, some Chinese married into the black and mulatto communities, as generally discrimination meant they did not take white spouses. They rapidly left working as laborers, and set up groceries in small towns throughout the South. They worked to get their children educated and socially mobile.
What cause wives to be unable to move to the US with their Chinese husbands after 1882?
A: the Chinese Exclusion Act

Context and question: Glacial moraines are formed by the deposition of material from a glacier and are exposed after the glacier has retreated. They usually appear as linear mounds of till, a non-sorted mixture of rock, gravel and boulders within a matrix of a fine powdery material. Terminal or end moraines are formed at the foot or terminal end of a glacier. Lateral moraines are formed on the sides of the glacier. Medial moraines are formed when two different glaciers merge and the lateral moraines of each coalesce to form a moraine in the middle of the combined glacier. Less apparent are ground moraines, also called glacial drift, which often blankets the surface underneath the glacier downslope from the equilibrium line.
What type of moraines are formed at the begining of the glacier?
Answer: unanswerable

Question: These areas contain some spectacular scenery as well, as evidenced by such national parks as Yosemite and Mount Rainier. West of the Cascades and Sierra Nevada is a series of valleys, such as the Central Valley in California and the Willamette Valley in Oregon. Along the coast is a series of low mountain ranges known as the Pacific Coast Ranges. Much of the Pacific Northwest coast is inhabited by some of the densest vegetation outside of the Tropics, and also the tallest trees in the world (the Redwoods).
Is there an answer to this question: What two national parks are located on the planes?

Answer: unanswerable

Plans for arena football were put on hold in 1982 as the United States Football League was launched. Foster left the NFL to accept a position in the USFL. He eventually became executive vice-president with the Chicago Blitz, where he returned to his concept of arena football. In 1983, he began organizing the test game in his spare time from his job with the Blitz. By 1985, the USFL had ceased football operations and he began devoting all his time to arena football, and on April 27, 1986, his concept was realized when the test game was played.
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): What was Foster's job title with the Chicago Blitz?
Ah, so..
executive vice-president