Problem: Glass:

Following the glass batch preparation and mixing, the raw materials are transported to the furnace. Soda-lime glass for mass production is melted in gas fired units. Smaller scale furnaces for specialty glasses include electric melters, pot furnaces, and day tanks. After melting, homogenization and refining (removal of bubbles), the glass is formed. Flat glass for windows and similar applications is formed by the float glass process, developed between 1953 and 1957 by Sir Alastair Pilkington and Kenneth Bickerstaff of the UK's Pilkington Brothers, who created a continuous ribbon of glass using a molten tin bath on which the molten glass flows unhindered under the influence of gravity. The top surface of the glass is subjected to nitrogen under pressure to obtain a polished finish. Container glass for common bottles and jars is formed by blowing and pressing methods. This glass is often slightly modified chemically (with more alumina and calcium oxide) for greater water resistance. Further glass forming techniques are summarized in the table Glass forming techniques.

What is used on the surface of window glass to make it smooth?
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A: nitrogen


Problem: It should be noted that Estonian words and names quoted in international publications from Soviet sources are often back-transliterations from the Russian transliteration. Examples are the use of "ya" for "ä" (e.g. Pyarnu instead of Pärnu), "y" instead of "õ" (e.g., Pylva instead of Põlva) and "yu" instead of "ü" (e.g., Pyussi instead of Püssi). Even in the Encyclopædia Britannica one can find "ostrov Khiuma", where "ostrov" means "island" in Russian and "Khiuma" is back-transliteration from Russian instead of "Hiiumaa" (Hiiumaa > Хийума(а) > Khiuma).
What is the Russian back-transliteration from Encyclopædia Britannica?
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Answer: "ostrov Khiuma"


Q: What is a question about this article? If the question is unanswerable, say "unanswerable".
In the 19th century, the city was transformed by development relating to its status as a trading center, as well as by European immigration. The city adopted the Commissioners' Plan of 1811, which expanded the city street grid to encompass all of Manhattan. The 1825 completion of the Erie Canal through central New York connected the Atlantic port to the agricultural markets and commodities of the North American interior via the Hudson River and the Great Lakes. Local politics became dominated by Tammany Hall, a political machine supported by Irish and German immigrants.
The Erie Canal was finished being built in what year?
A: 1825


Context and question: Throughout its history, the city has been a major port of entry for immigrants into the United States; more than 12 million European immigrants were received at Ellis Island between 1892 and 1924. The term "melting pot" was first coined to describe densely populated immigrant neighborhoods on the Lower East Side. By 1900, Germans constituted the largest immigrant group, followed by the Irish, Jews, and Italians. In 1940, whites represented 92% of the city's population.
What ethnicity comprised the largest number of immigrants at the beginning of the twentieth century?
Answer: Germans


Question: The northern side of the borough includes the largest park in New York City—Pelham Bay Park, which includes Orchard Beach—and the fourth largest, Van Cortlandt Park, which is west of Woodlawn Cemetery and borders Yonkers. Also in the northern Bronx, Wave Hill, the former estate of George W. Perkins—known for a historic house, gardens, changing site-specific art installations and concerts—overlooks the New Jersey Palisades from a promontory on the Hudson in Riverdale. Nearer the borough's center, and along the Bronx River, is Bronx Park; its northern end houses the New York Botanical Gardens, which preserve the last patch of the original hemlock forest that once covered the entire county, and its southern end the Bronx Zoo, the largest urban zoological gardens in the United States. Just south of Van Cortlandt Park is the Jerome Park Reservoir, surrounded by 2 miles (3 km) of stone walls and bordering several small parks in the Bedford Park neighborhood; the reservoir was built in the 1890s on the site of the former Jerome Park Racetrack. Further south is Crotona Park, home to a 3.3-acre (1.3 ha) lake, 28 species of trees, and a large swimming pool. The land for these parks, and many others, was bought by New York City in 1888, while land was still open and inexpensive, in anticipation of future needs and future pressures for development.
Is there an answer to this question: How many types of trees are in Crotona Park?

Answer: 28


Problem: Mexico City:

The National Autonomous University of Mexico (UNAM), located in Mexico City, is the largest university on the continent, with more than 300,000 students from all backgrounds. Three Nobel laureates, several Mexican entrepreneurs and most of Mexico's modern-day presidents are among its former students. UNAM conducts 50% of Mexico's scientific research and has presence all across the country with satellite campuses, observatories and research centres. UNAM ranked 74th in the Top 200 World University Ranking published by Times Higher Education (then called Times Higher Education Supplement) in 2006, making it the highest ranked Spanish-speaking university in the world. The sprawling main campus of the university, known as Ciudad Universitaria, was named a World Heritage Site by UNESCO in 2007.

What is the main campus of UNAM called?
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A:
Ciudad Universitaria