Here is a question about this article: Areas such as South Street and Old City have a vibrant night life. The Avenue of the Arts in Center City contains many restaurants and theaters, such as the Kimmel Center for the Performing Arts, which is home to the Philadelphia Orchestra, generally considered one of the top five orchestras in the United States, and the Academy of Music, the nation's oldest continually operating opera house, home to the Opera Company of Philadelphia and the Pennsylvania Ballet. The Wilma Theatre and Philadelphia Theatre Company have new buildings constructed in the last decade on the avenue. They produce a variety of new works. Several blocks to the east are the Walnut Street Theatre, America's oldest theatre and the largest subscription theater in the world; as well as the Lantern Theatre at St. Stephens Church, one of a number of smaller venues.
What is the answer to this question: What is the oldest theater in the U.S.?
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So... Walnut Street Theatre

Here is a question about this article: Other sections of society included the nobility, clergy, and townsmen. Nobles, both the titled nobility and simple knights, exploited the manors and the peasants, although they did not own lands outright but were granted rights to the income from a manor or other lands by an overlord through the system of feudalism. During the 11th and 12th centuries, these lands, or fiefs, came to be considered hereditary, and in most areas they were no longer divisible between all the heirs as had been the case in the early medieval period. Instead, most fiefs and lands went to the eldest son.[R] The dominance of the nobility was built upon its control of the land, its military service as heavy cavalry, control of castles, and various immunities from taxes or other impositions.[S] Castles, initially in wood but later in stone, began to be constructed in the 9th and 10th centuries in response to the disorder of the time, and provided protection from invaders as well as allowing lords defence from rivals. Control of castles allowed the nobles to defy kings or other overlords. Nobles were stratified; kings and the highest-ranking nobility controlled large numbers of commoners and large tracts of land, as well as other nobles. Beneath them, lesser nobles had authority over smaller areas of land and fewer people. Knights were the lowest level of nobility; they controlled but did not own land, and had to serve other nobles.[T]
What is the answer to this question: In what centuries did fiefs become hereditary?
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So... 11th and 12th

Here is a question about this article: Biomass for heat and power is a fully mature technology which offers a ready disposal mechanism for municipal, agricultural, and industrial organic wastes. However, the industry has remained relatively stagnant over the decade to 2007, even though demand for biomass (mostly wood) continues to grow in many developing countries. One of the problems of biomass is that material directly combusted in cook stoves produces pollutants, leading to severe health and environmental consequences, although improved cook stove programmes are alleviating some of these effects. First-generation biomass technologies can be economically competitive, but may still require deployment support to overcome public acceptance and small-scale issues.
What is the answer to this question: What can be economically competetive but may still require deployment support?
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So...
First-generation biomass technologies