Problem: London:

Other mammals found in Greater London are hedgehogs, rats, mice, rabbit, shrew, vole, and squirrels, In wilder areas of Outer London, such as Epping Forest, a wide variety of mammals are found including hare, badger, field, bank and water vole, wood mouse, yellow-necked mouse, mole, shrew, and weasel, in addition to fox, squirrel and hedgehog. A dead otter was found at The Highway, in Wapping, about a mile from the Tower Bridge, which would suggest that they have begun to move back after being absent a hundred years from the city. Ten of England's eighteen species of bats have been recorded in Epping Forest: soprano, nathusius and common pipistrelles, noctule, serotine, barbastelle, daubenton's, brown Long-eared, natterer's and leisler's.

It appears that otters may be returning to the city of London after how long an absence?
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A: a hundred years

Problem: Department store:

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 Germany operated?
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A: London, Paris and New York.

Problem: Glass:

The most familiar, and historically the oldest, types of glass are "silicate glasses" based on the chemical compound silica (silicon dioxide, or quartz), the primary constituent of sand. The term glass, in popular usage, is often used to refer only to this type of material, which is familiar from use as window glass and in glass bottles. Of the many silica-based glasses that exist, ordinary glazing and container glass is formed from a specific type called soda-lime glass, composed of approximately 75% silicon dioxide (SiO2), sodium oxide (Na2O) from sodium carbonate (Na2CO3), calcium oxide, also called lime (CaO), and several minor additives. A very clear and durable quartz glass can be made from pure silica, but the high melting point and very narrow glass transition of quartz make glassblowing and hot working difficult. In glasses like soda lime, the compounds added to quartz are used to lower the melting temperature and improve workability, at a cost in the toughness, thermal stability, and optical transmittance.

What types of glass is the word commonly used to mean?
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A: silicate glasses

Problem: Gregorian calendar:

In conjunction with the system of months there is a system of weeks. A physical or electronic calendar provides conversion from a given date to the weekday, and shows multiple dates for a given weekday and month. Calculating the day of the week is not very simple, because of the irregularities in the Gregorian system. When the Gregorian calendar was adopted by each country, the weekly cycle continued uninterrupted. For example, in the case of the few countries that adopted the reformed calendar on the date proposed by Gregory XIII for the calendar's adoption, Friday, 15 October 1582, the preceding date was Thursday, 4 October 1582 (Julian calendar).

Why is calculating the days of the Gregorian calendar not simple?
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A:
irregularities