The problem: Answer a question about this article:
Equivalently, the smallness of the Planck constant reflects the fact that everyday objects and systems are made of a large number of particles. For example, green light with a wavelength of 555 nanometres (the approximate wavelength to which human eyes are most sensitive) has a frequency of 7014540000000000000♠️540 THz (7014540000000000000♠️5401012 Hz). Each photon has an energy E = hf = 6981358000000000000♠️3.581019 J. That is a very small amount of energy in terms of everyday experience, but everyday experience is not concerned with individual photons any more than with individual atoms or molecules. An amount of light compatible with everyday experience is the energy of one mole of photons; its energy can be computed by multiplying the photon energy by the Avogadro constant, NA 7023602200000000000♠️6.0221023 mol1. The result is that green light of wavelength 555 nm has an energy of 7005216000000000000♠️216 kJ/mol, a typical energy of everyday life.
What is the frequency of the light to which the human eye is most sensitive?
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The answer: 7014540000000000000♠️540 THz

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Unmarked vehicles are used primarily for sting operations or apprehending criminals without alerting them to their presence. Some police forces use unmarked or minimally marked cars for traffic law enforcement, since drivers slow down at the sight of marked police vehicles and unmarked vehicles make it easier for officers to catch speeders and traffic violators. This practice is controversial, with for example, New York State banning this practice in 1996 on the grounds that it endangered motorists who might be pulled over by people impersonating police officers.
Why did New York State ban unmarked cars for traffic cops?
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The answer: it endangered motorists who might be pulled over by people impersonating police officers

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The morphology of Catalan personal pronouns is complex, specially in unstressed forms, which are numerous (13 distinct forms, compared to 11 in Spanish or 9 in Italian). Features include the gender-neutral ho and the great degree of freedom when combining different unstressed pronouns (65 combinations).
How many different combinations of unstressed pronouns are there?
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The answer: 65

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Political and religious animosity against Jehovah's Witnesses has at times led to mob action and government oppression in various countries. Their doctrine of political neutrality and their refusal to serve in the military has led to imprisonment of members who refused conscription during World War II and at other times where national service has been compulsory. In 1933, there were approximately 20,000 Jehovah's Witnesses in Germany, of whom about 10,000 were later imprisoned. Of those, 2000 were sent to Nazi concentration camps, where they were identified by purple triangles; as many as 1200 died, including 250 who were executed. In Canada, Jehovah's Witnesses were interned in camps along with political dissidents and people of Chinese and Japanese descent. In the former Soviet Union, about 9,300 Jehovah's Witnesses were deported to Siberia as part of Operation North in April 1951. Their religious activities are currently banned or restricted in some countries, including China, Vietnam and some Islamic states.
Of the 20,000 Jehovah's Witnesses in Germany in 1933, how many were later imprisoned?
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The answer:
10,000