Problem: Incandescent light bulb:

The spectrum emitted by a blackbody radiator at temperatures of incandescent bulbs does not match the sensitivity characteristics of the human eye; the light emitted does not appear white, and most is not in the range of wavelengths at which the eye is most sensitive. Tungsten filaments radiate mostly infrared radiation at temperatures where they remain solid below 3,695 K (3,422 C; 6,191 F). Donald L. Klipstein explains it this way: "An ideal thermal radiator produces visible light most efficiently at temperatures around 6,300 C (6,600 K; 11,400 F). Even at this high temperature, a lot of the radiation is either infrared or ultraviolet, and the theoretical luminous efficacy (LER) is 95 lumens per watt." No known material can be used as a filament at this ideal temperature, which is hotter than the sun's surface. An upper limit for incandescent lamp luminous efficacy (LER) is around 52 lumens per watt, the theoretical value emitted by tungsten at its melting point.

What does not radiate mostly infrared radiation at temperatures where they remain solid?
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A: unanswerable

Problem: What is today the Central African Republic has been inhabited for millennia; however, the country's current borders were established by France, which ruled the country as a colony starting in the late 19th century. After gaining independence from France in 1960, the Central African Republic was ruled by a series of autocratic leaders; by the 1990s, calls for democracy led to the first multi-party democratic elections in 1993. Ange-Felix Patasse became president, but was later removed by General Francois Bozize in the 2003 coup. The Central African Republic Bush War began in 2004 and, despite a peace treaty in 2007 and another in 2011, fighting broke out between various factions in December 2012, leading to ethnic and religious cleansing of the Muslim minority and massive population displacement in 2013 and 2014.
Who established CAR's borders?
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Answer: France

Q: What is a question about this article? If the question is unanswerable, say "unanswerable".
Elevators necessitated new social protocols. When Nicholas II of Russia visited the Hotel Adlon in Berlin, his courtiers panicked about who would enter the elevator first, and who would press the buttons. In Lifted: A Cultural History of the Elevator, author Andreas Bernard documents other social impacts caused by the modern elevator, including thriller movies about stuck elevators, casual encounters and sexual tension on elevators, the reduction of personal space, and concerns about personal hygiene.
This caused a stir in deciding who should enter first and who should do what?
A: press the buttons

Context and question: In contemporary society, adolescents also face some risks as their sexuality begins to transform. While some of these, such as emotional distress (fear of abuse or exploitation) and sexually transmitted infections/diseases (STIs/STDs), including HIV/AIDS, are not necessarily inherent to adolescence, others such as teenage pregnancy (through non-use or failure of contraceptives) are seen as social problems in most western societies. One in four sexually active teenagers will contract an STI. Adolescents in the United States often chose "anything but intercourse" for sexual activity because they mistakenly believe it reduces the risk of STIs. Across the country, clinicians report rising diagnoses of herpes and human papillomavirus (HPV), which can cause genital warts, and is now thought to affect 15 percent of the teen population. Girls 15 to 19 have higher rates of gonorrhea than any other age group. One-quarter of all new HIV cases occur in those under the age of 21. Multrine also states in her article that according to a March survey by the Kaiser Family Foundation, eighty-one percent of parents want schools to discuss the use of condoms and contraception with their children. They also believe students should be able to be tested for STIs. Furthermore, teachers want to address such topics with their students. But, although 9 in 10 sex education instructors across the country believe that students should be taught about contraceptives in school, over one quarter report receiving explicit instructions from school boards and administrators not to do so. According to anthropologist Margaret Mead, the turmoil found in adolescence in Western society has a cultural rather than a physical cause; they reported that societies where young women engaged in free sexual activity had no such adolescent turmoil.
According to a survey by the Kaiser Family Foundation, what percentage of parents want schools to discuss contraception with their children?
Answer: eighty-one percent

Question: The semi-finals have been played exclusively at the rebuilt Wembley Stadium since 2008, one year after it opened and after it had already hosted a final (in 2007). For the first decade of the competition, the Kennington Oval was used as the semi-final venue. In the period between this first decade and the reopening of Wembley, semi-finals were played at high-capacity neutral venues around England; usually the home grounds of teams not involved in that semi-final, chosen to be roughly equidistant between the two teams for fairness of travel. The top three most used venues in this period were Villa Park in Birmingham (55 times), Hillsborough in Sheffield (34 times) and Old Trafford in Manchester (23 times). The original Wembley Stadium was also used seven times for semi-final, between 1991 and 2000 (the last held there), but not always for fixtures featuring London teams. In 2005, both were held at the Millennium Stadium.
Is there an answer to this question: Where are the semi-finals never played?

Answer: unanswerable

Q: What is a question about this article? If the question is unanswerable, say "unanswerable".
Connaught Place, one of North India's largest commercial and financial centres, is located in the northern part of New Delhi. Adjoining areas such as Barakhamba Road, ITO are also major commercial centres. Government and quasi government sector was the primary employer in New Delhi. The city's service sector has expanded due in part to the large skilled English-speaking workforce that has attracted many multinational companies. Key service industries include information technology, telecommunications, hotels, banking, media and tourism.
The large skilled English-speaking workforce of New Delhi has been able to attract what type of organizations to the city?
A:
multinational companies