Problem: Printed circuit board:

Initially PCBs were designed manually by creating a photomask on a clear mylar sheet, usually at two or four times the true size. Starting from the schematic diagram the component pin pads were laid out on the mylar and then traces were routed to connect the pads. Rub-on dry transfers of common component footprints increased efficiency. Traces were made with self-adhesive tape. Pre-printed non-reproducing grids on the mylar assisted in layout. To fabricate the board, the finished photomask was photolithographically reproduced onto a photoresist coating on the blank copper-clad boards.

Self-adhesive mylar was used to make what?
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A: unanswerable


Problem: Naturally occurring crude asphalt/bitumen impregnated in sedimentary rock is the prime feed stock for petroleum production from "Oil sands", currently under development in Alberta, Canada. Canada has most of the world's supply of natural asphalt/bitumen, covering 140,000 square kilometres (an area larger than England), giving it the second-largest proven oil reserves in the world. The Athabasca oil sands is the largest asphalt/bitumen deposit in Canada and the only one accessible to surface mining, although recent technological breakthroughs have resulted in deeper deposits becoming producible by in situ methods. Because of oil price increases after 2003, producing bitumen became highly profitable, but as a result of the decline after 2014 it became uneconomic to build new plants again. By 2014, Canadian crude asphalt/bitumen production averaged about 2.3 million barrels (370,000 m3) per day and was projected to rise to 4.4 million barrels (700,000 m3) per day by 2020. The total amount of crude asphalt/bitumen in Alberta which could be extracted is estimated to be about 310 billion barrels (50×10^9 m3), which at a rate of 4,400,000 barrels per day (700,000 m3/d) would last about 200 years.
By what year did Athabascan crude asphalt/bitumen production average 2.3 million barrels per day?
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Answer: unanswerable


Q: What is a question about this article? If the question is unanswerable, say "unanswerable".
DC commutating electric motors, if fitted with laminated pole pieces, become universal motors because they can also operate on AC; reversing the current in both stator and rotor does not reverse the motor. But the now-standard AC distribution frequencies of 50 and 60 Hz caused difficulties with inductive reactance and eddy current losses. Many railways chose low AC frequencies to overcome these problems. They must be converted from utility power by motor-generators or static inverters at the feeding substations or generated at dedicated traction powerstations.
How can low frequencies be obtained?
A: converted from utility power


Context and question: The word phonology comes from the Greek φωνή, phōnḗ, "voice, sound," and the suffix -logy (which is from Greek λόγος, lógos, "word, speech, subject of discussion"). Definitions of the term vary. Nikolai Trubetzkoy in Grundzüge der Phonologie (1939) defines phonology as "the study of sound pertaining to the system of language," as opposed to phonetics, which is "the study of sound pertaining to the act of speech" (the distinction between language and speech being basically Saussure's distinction between langue and parole). More recently, Lass (1998) writes that phonology refers broadly to the subdiscipline of linguistics concerned with the sounds of language, while in more narrow terms, "phonology proper is concerned with the function, behavior and organization of sounds as linguistic items." According to Clark et al. (2007), it means the systematic use of sound to encode meaning in any spoken human language, or the field of linguistics studying this use.
When did Lass write about phonology?
Answer: 1998


Question: About half of the population depends on agriculture (largely subsistence agriculture) for its livelihood, but Namibia must still import some of its food. Although per capita GDP is five times the per capita GDP of Africa's poorest countries, the majority of Namibia's people live in rural areas and exist on a subsistence way of life. Namibia has one of the highest rates of income inequality in the world, due in part to the fact that there is an urban economy and a more rural cash-less economy. The inequality figures thus take into account people who do not actually rely on the formal economy for their survival. Although arable land accounts for only 1% of Namibia, nearly half of the population is employed in agriculture.
Is there an answer to this question: In Africa's poorest countries in which industry do most people work?

Answer: unanswerable


Question: Tajikistan has a population of 7,349,145 (July 2009 est.) of which 70% are under the age of 30 and 35% are between the ages of 14 and 30. Tajiks who speak Tajik (a dialect of Persian) are the main ethnic group, although there are sizable minorities of Uzbeks and Russians, whose numbers are declining due to emigration. The Pamiris of Badakhshan, a small population of Yaghnobi people, and a sizeable minority of Ismailis are all considered to belong to the larger group of Tajiks. All citizens of Tajikistan are called Tajikistanis.
Is there an answer to this question: What percent of the population are between 14 to 30 years old?

Answer:
35%