Q: What is a question about this article? If the question is unanswerable, say "unanswerable".
In the late 20th century a new concept was added to those included in the compass of both structure and function, the consideration of sustainability, hence sustainable architecture. To satisfy the contemporary ethos a building should be constructed in a manner which is environmentally friendly in terms of the production of its materials, its impact upon the natural and built environment of its surrounding area and the demands that it makes upon non-sustainable power sources for heating, cooling, water and waste management and lighting.
What sort of power sources should a building not overuse if the building is to be considered environmentally friendly?
A: non-sustainable power sources

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Many bird populations migrate long distances along a flyway. The most common pattern involves flying north in the spring to breed in the temperate or Arctic summer and returning in the autumn to wintering grounds in warmer regions to the south. Of course, in the southern hemisphere the directions are reversed, but there is less land area in the far south to support long-distance migration.
What is the most common directionof migration in autumn?
A: south

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Gaddafi briefly studied History at the University of Libya in Benghazi, before dropping out to join the military. Despite his police record, in 1963 he began training at the Royal Military Academy, Benghazi, alongside several like-minded friends from Misrata. The armed forces offered the only opportunity for upward social mobility for underprivileged Libyans, and Gaddafi recognised it as a potential instrument of political change. Under Idris, Libya's armed forces were trained by the British military; this angered Gaddafi, who viewed the British as imperialists, and accordingly he refused to learn English and was rude to the British officers, ultimately failing his exams. British trainers reported him for insubordination and abusive behaviour, stating their suspicion that he was involved in the assassination of the military academy's commander in 1963. Such reports were ignored and Gaddafi quickly progressed through the course.
Why didn't Gaddafi learn to speak English?
A: Gaddafi, who viewed the British as imperialists

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A key component common to all CPUs is the program counter, a special memory cell (a register) that keeps track of which location in memory the next instruction is to be read from.
A special memory cell of a CPU is called what?
A:
a register