Problem: Umayyad Caliphate:

Mu'awiyah introduced postal service, Abd al-Malik extended it throughout his empire, and Walid made full use of it. The Umayyad Caliph Abd al-Malik developed a regular postal service. Umar bin Abdul-Aziz developed it further by building caravanserais at stages along the Khurasan highway. Relays of horses were used for the conveyance of dispatches between the caliph and his agents and officials posted in the provinces. The main highways were divided into stages of 12 miles (19 km) each and each stage had horses, donkeys or camels ready to carry the post. Primarily the service met the needs of Government officials, but travellers and their important dispatches were also benefitted by the system. The postal carriages were also used for the swift transport of troops. They were able to carry fifty to a hundred men at a time. Under Governor Yusuf bin Umar, the postal department of Iraq cost 4,000,000 dirhams a year.

Along what highway did Umar bin Abdul-Aziz build caravanserais?
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A: Khurasan

Problem: Earthworms are Oligochaetes that support terrestrial food chains both as prey and in some regions are important in aeration and enriching of soil. The burrowing of marine polychaetes, which may constitute up to a third of all species in near-shore environments, encourages the development of ecosystems by enabling water and oxygen to penetrate the sea floor. In addition to improving soil fertility, annelids serve humans as food and as bait. Scientists observe annelids to monitor the quality of marine and fresh water. Although blood-letting is no longer in favor with doctors, some leech species are regarded as endangered species because they have been over-harvested for this purpose in the last few centuries. Ragworms' jaws are now being studied by engineers as they offer an exceptional combination of lightness and strength.
How do burrowing marine annelids remove ocean ecosystems?
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Answer: unanswerable

Q: What is a question about this article? If the question is unanswerable, say "unanswerable".
The metal's distinctive natural green patina has long been coveted by architects and designers. The final patina is a particularly durable layer that is highly resistant to atmospheric corrosion, thereby protecting the underlying metal against further weathering. It can be a mixture of carbonate and sulfate compounds in various amounts, depending upon environmental conditions such as sulfur-containing acid rain. Architectural copper and its alloys can also be 'finished' to embark a particular look, feel, and/or color. Finishes include mechanical surface treatments, chemical coloring, and coatings.
What mixture of compounds is the final patina?
A: carbonate and sulfate

Context and question: The design and function of department stores in Germany followed the lead of London, Paris and New York. Germany used to have a number of department stores; nowadays only a few of them remain. Next to some smaller, independent department stores these are Karstadt (in 2010 taken over by Nicolas Berggruen, also operating the KaDeWe in Berlin, the Alsterhaus in Hamburg and the Oberpollinger in Munich), GALERIA Kaufhof (part of the Metro AG). Others like Hertie, Wertheim and Horten AG were taken over by others and either fully integrated or later closed.
What cities influenced how department stores in Austria operated?
Answer: unanswerable

Question: On October 17, 1987, about 3,000 Armenians demonstrated in Yerevan complaining about the condition of Lake Sevan, the Nairit chemicals plant, and the Metsamor Nuclear Power Plant, and air pollution in Yerevan. Police tried to prevent the protest but took no action to stop it once the march was underway. The demonstration was led by Armenian writers such as Silva Kaputikian, Zori Balayan, and Maro Margarian and leaders from the National Survival organization. The march originated at the Opera Plaza after speakers, mainly intellectuals, addressed the crowd.
Is there an answer to this question: The protesters were unhappy with the pollution in what body of water?

Answer: Lake Sevan

Problem: Yale University:

Milton Winternitz led the Yale Medical School as its dean from 1920 to 1935. Dedicated to the new scientific medicine established in Germany, he was equally fervent about "social medicine" and the study of humans in their culture and environment. He established the "Yale System" of teaching, with few lectures and fewer exams, and strengthened the full-time faculty system; he also created the graduate-level Yale School of Nursing and the Psychiatry Department, and built numerous new buildings. Progress toward his plans for an Institute of Human Relations, envisioned as a refuge where social scientists would collaborate with biological scientists in a holistic study of humankind, unfortunately lasted for only a few years before the opposition of resentful anti-Semitic colleagues drove him to resign.

What wasn't the driving force behind Milton Winternitz's research?
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A:
unanswerable