TASK DEFINITION: This task is about reading the given passage and construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) its answer is a continuous text span from the paragraph. Avoid creating questions that (i) can be answered correctly without actually understanding the paragraph and (ii) uses same words or phrases given in the passage.
PROBLEM: In the Western Balkans, South Slavs and Germanic Gepids intermarried with Avar invaders, eventually producing a Slavicized population.[citation needed] In Central Europe, the Slavs intermixed with Germanic and Celtic, while the eastern Slavs encountered Uralic and Scandinavian peoples. Scandinavians (Varangians) and Finnic peoples were involved in the early formation of the Rus' state but were completely Slavicized after a century. Some Finno-Ugric tribes in the north were also absorbed into the expanding Rus population. At the time of the Magyar migration, the present-day Hungary was inhabited by Slavs, numbering about 200,000, and by Romano-Dacians who were either assimilated or enslaved by the Magyars. In the 11th and 12th centuries, constant incursions by nomadic Turkic tribes, such as the Kipchaks and the Pechenegs, caused a massive migration of East Slavic populations to the safer, heavily forested regions of the north. In the Middle Ages, groups of Saxon ore miners settled in medieval Bosnia, Serbia and Bulgaria where they were Slavicized.

SOLUTION: Where did South Slavs and Germanic Gepids intermarried with Avar invaders?

PROBLEM: Many applications of silicate glasses derive from their optical transparency, which gives rise to one of silicate glasses' primary uses as window panes. Glass will transmit, reflect and refract light; these qualities can be enhanced by cutting and polishing to make optical lenses, prisms, fine glassware, and optical fibers for high speed data transmission by light. Glass can be colored by adding metallic salts, and can also be painted and printed with vitreous enamels. These qualities have led to the extensive use of glass in the manufacture of art objects and in particular, stained glass windows. Although brittle, silicate glass is extremely durable, and many examples of glass fragments exist from early glass-making cultures. Because glass can be formed or molded into any shape, and also because it is a sterile product, it has been traditionally used for vessels: bowls, vases, bottles, jars and drinking glasses. In its most solid forms it has also been used for paperweights, marbles, and beads. When extruded as glass fiber and matted as glass wool in a way to trap air, it becomes a thermal insulating material, and when these glass fibers are embedded into an organic polymer plastic, they are a key structural reinforcement part of the composite material fiberglass. Some objects historically were so commonly made of silicate glass that they are simply called by the name of the material, such as drinking glasses and reading glasses.

SOLUTION: What ingredient makes glass colorful?

PROBLEM: After leaving Edison's company Tesla partnered with two businessmen in 1886, Robert Lane and Benjamin Vail, who agreed to finance an electric lighting company in Tesla's name, Tesla Electric Light & Manufacturing. The company installed electrical arc light based illumination systems designed by Tesla and also had designs for dynamo electric machine commutators, the first patents issued to Tesla in the US.

SOLUTION:
Who did Tesla partner with in 1886?