Problem: Glass:

Fused quartz is a glass made from chemically-pure SiO2 (silica). It has excellent thermal shock characteristics, being able to survive immersion in water while red hot. However, its high melting-temperature (1723 °C) and viscosity make it difficult to work with. Normally, other substances are added to simplify processing. One is sodium carbonate (Na2CO3, "soda"), which lowers the glass transition temperature. The soda makes the glass water-soluble, which is usually undesirable, so lime (calcium oxide [CaO], generally obtained from limestone), some magnesium oxide (MgO) and aluminium oxide (Al2O3) are added to provide for a better chemical durability. The resulting glass contains about 70 to 74% silica by weight and is called a soda-lime glass. Soda-lime glasses account for about 90% of manufactured glass.

Why is lime often added to glass?
---
A: better chemical durability


Problem: 112th Street starts in Morningside Heights and runs from Riverside Drive to Amsterdam Avenue, where it meets the steps of the Cathedral of Saint John the Divine. The street resumes at the eastern edge of Morningside Park and extends through Harlem before ending at First Avenue adjacent Thomas Jefferson Park in East Harlem. Notable locations include:
Where does 112th Street start?
---
Answer: Morningside Heights


Q: What is a question about this article? If the question is unanswerable, say "unanswerable".
The first Europeans to disembark and explore the region were the Portuguese navigators Diogo Cão in 1485 and Bartolomeu Dias in 1486; still the region was not claimed by the Portuguese crown. However, like most of Sub-Saharan Africa, Namibia was not extensively explored by Europeans until the 19th century, when traders and settlers arrived, principally from Germany and Sweden. In the late 19th century Dorsland trekkers crossed the area on their way from the Transvaal to Angola. Some of them settled in Namibia instead of continuing their journey.
When did Diogo Cao explore Namibia?
A: 1485


Context and question: In most US and Canadian jurisdictions, passenger elevators are required to conform to the American Society of Mechanical Engineers' Standard A17.1, Safety Code for Elevators and Escalators. As of 2006, all states except Kansas, Mississippi, North Dakota, and South Dakota have adopted some version of ASME codes, though not necessarily the most recent. In Canada the document is the CAN/CSA B44 Safety Standard, which was harmonized with the US version in the 2000 edition.[citation needed] In addition, passenger elevators may be required to conform to the requirements of A17.3 for existing elevators where referenced by the local jurisdiction. Passenger elevators are tested using the ASME A17.2 Standard. The frequency of these tests is mandated by the local jurisdiction, which may be a town, city, state or provincial standard.
 What is Standard A17.1?
Answer: Safety Code for Elevators and Escalators


Question: Sichuan has been historically known as the "Province of Abundance". It is one of the major agricultural production bases of China. Grain, including rice and wheat, is the major product with output that ranked first in China in 1999. Commercial crops include citrus fruits, sugar cane, sweet potatoes, peaches and grapes. Sichuan also had the largest output of pork among all the provinces and the second largest output of silkworm cocoons in 1999. Sichuan is rich in mineral resources. It has more than 132 kinds of proven underground mineral resources including vanadium, titanium, and lithium being the largest in China. The Panxi region alone possesses 13.3% of the reserves of iron, 93% of titanium, 69% of vanadium, and 83% of the cobalt of the whole country. Sichuan also possesses China's largest proven natural gas reserves, the majority of which is transported to more developed eastern regions.
Is there an answer to this question: What region contains 69% of the titanium  reserves?

Answer: unanswerable


Problem: Tristan da Cunha:

In 1958 as part of an experiment, Operation Argus, the United States Navy detonated an atomic bomb 160 kilometres (100 mi) high in the upper atmosphere about 175 kilometres (109 mi) southeast of the main island.

What country test detonated an atomic bomb near the island?
---
A:
United States