Problem: Mandolin:

There are many styles of mandolin, but four are common, the Neapolitan or round-backed mandolin, the carved-top mandolin and the flat-backed mandolin. The round-back has a deep bottom, constructed of strips of wood, glued together into a bowl. The carved-top or arch-top mandolin has a much shallower, arched back, and an arched top—both carved out of wood. The flat-backed mandolin uses thin sheets of wood for the body, braced on the inside for strength in a similar manner to a guitar. Each style of instrument has its own sound quality and is associated with particular forms of music. Neapolitan mandolins feature prominently in European classical music and traditional music. Carved-top instruments are common in American folk music and bluegrass music. Flat-backed instruments are commonly used in Irish, British and Brazilian folk music. Some modern Brazilian instruments feature an extra fifth course tuned a fifth lower than the standard fourth course.

 What is the round-front mandolin made of?
---
A: unanswerable


Problem: The first blue-violet LED using magnesium-doped gallium nitride was made at Stanford University in 1972 by Herb Maruska and Wally Rhines, doctoral students in materials science and engineering. At the time Maruska was on leave from RCA Laboratories, where he collaborated with Jacques Pankove on related work. In 1971, the year after Maruska left for Stanford, his RCA colleagues Pankove and Ed Miller demonstrated the first blue electroluminescence from zinc-doped gallium nitride, though the subsequent device Pankove and Miller built, the first actual gallium nitride light-emitting diode, emitted green light. In 1974 the U.S. Patent Office awarded Maruska, Rhines and Stanford professor David Stevenson a patent for their work in 1972 (U.S. Patent US3819974 A) and today magnesium-doping of gallium nitride continues to be the basis for all commercial blue LEDs and laser diodes. These devices built in the early 1970s had too little light output to be of practical use and research into gallium nitride devices slowed. In August 1989, Cree introduced the first commercially available blue LED based on the indirect bandgap semiconductor, silicon carbide (SiC). SiC LEDs had very low efficiency, no more than about 0.03%, but did emit in the blue portion of the visible light spectrum.[citation needed]
 What students developed the first red-violet LED?
---
Answer: unanswerable


Q: What is a question about this article? If the question is unanswerable, say "unanswerable".
The court noted that it "is a matter of history that this very practice of establishing governmentally composed prayers for religious services was one of the reasons which caused many of our early colonists to leave England and seek religious freedom in America." The lone dissenter, Justice Potter Stewart, objected to the court's embrace of the "wall of separation" metaphor: "I think that the Court's task, in this as in all areas of constitutional adjudication, is not responsibly aided by the uncritical invocation of metaphors like the "wall of separation," a phrase nowhere to be found in the Constitution."
Stewart pointed out that the phrase "Wall of separation" was everywhere to be found in what?
A: unanswerable


Context and question: The main crops grown are barley, wheat, buckwheat, rye, potatoes, and assorted fruits and vegetables. Tibet is ranked the lowest among China’s 31 provinces on the Human Development Index according to UN Development Programme data. In recent years, due to increased interest in Tibetan Buddhism, tourism has become an increasingly important sector, and is actively promoted by the authorities. Tourism brings in the most income from the sale of handicrafts. These include Tibetan hats, jewelry (silver and gold), wooden items, clothing, quilts, fabrics, Tibetan rugs and carpets. The Central People's Government exempts Tibet from all taxation and provides 90% of Tibet's government expenditures. However most of this investment goes to pay migrant workers who do not settle in Tibet and send much of their income home to other provinces.
Where is Tibet ranked among China's 31 provinces on the UN's Human Development Index?
Answer: lowest


Question: The term "Late Middle Ages" refers to one of the three periods of the Middle Ages, along with the Early Middle Ages and the High Middle Ages. Leonardo Bruni was the first historian to use tripartite periodization in his History of the Florentine People (1442). Flavio Biondo used a similar framework in Decades of History from the Deterioration of the Roman Empire (1439–1453). Tripartite periodization became standard after the German historian Christoph Cellarius published Universal History Divided into an Ancient, Medieval, and New Period (1683).
Is there an answer to this question: When was Leonardo Bruni's "History of the Florentine People" published?

Answer: 1442


QUES: Although Mali has enjoyed a reasonably good inter-ethnic relationships based on the long history of coexistence, some hereditary servitude and bondage relationship exist, as well as ethnic tension between settled Songhai and nomadic Tuaregs of the north. Due to a backlash against the northern population after independence, Mali is now in a situation where both groups complain about discrimination on the part of the other group. This conflict also plays a role in the continuing Northern Mali conflict where there is a tension between both Tuaregs and the Malian government, and the Tuaregs and radical Islamists who are trying to establish sharia law.

What plays a role in the tension between the Soanghai and the government?
What is the answer?
ANS:
unanswerable