Problem: Philadelphia:

Since the early days of rail transport in the United States, Philadelphia has served as hub for several major rail companies, particularly the Pennsylvania Railroad and the Reading Railroad. The Pennsylvania Railroad first operated Broad Street Station, then 30th Street Station and Suburban Station, and the Reading Railroad operated out of Reading Terminal, now part of the Pennsylvania Convention Center. The two companies also operated competing commuter rail systems in the area, known collectively as the Regional Rail system. The two systems today, for the most part still intact but now connected, operate as a single system under the control of the SEPTA, the regional transit authority. Additionally, the PATCO Speedline subway system and NJ Transit's Atlantic City Line operate successor services to southern New Jersey.

Name 2 rail companies that use the city as a hub?
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A: Pennsylvania Railroad and the Reading Railroad

Problem: Police:

All police officers in the United Kingdom, whatever their actual rank, are 'constables' in terms of their legal position. This means that a newly appointed constable has the same arrest powers as a Chief Constable or Commissioner. However, certain higher ranks have additional powers to authorize certain aspects of police operations, such as a power to authorize a search of a suspect's house (section 18 PACE in England and Wales) by an officer of the rank of Inspector, or the power to authorize a suspect's detention beyond 24 hours by a Superintendent.

What can only Superintendent-ranked UK officers do?
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A: authorize a suspect's detention beyond 24 hours

Problem: Samurai:

The Japanese defenders recognized the possibility of a renewed invasion, and began construction of a great stone barrier around Hakata Bay in 1276. Completed in 1277, this wall stretched for 20 kilometers around the border of the bay. This would later serve as a strong defensive point against the Mongols. The Mongols attempted to settle matters in a diplomatic way from 1275 to 1279, but every envoy sent to Japan was executed. This set the stage for one of the most famous engagements in Japanese history.

How long was the Hakata Bay barrier?
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A: 20 kilometers

Problem: Adolescence:

Dating violence is fairly prevalent within adolescent relationships. When surveyed, 10-45% of adolescents reported having experienced physical violence in the context of a relationship while a quarter to a third of adolescents reported having experiencing psychological aggression. This reported aggression includes hitting, throwing things, or slaps, although most of this physical aggression does not result in a medical visit. Physical aggression in relationships tends to decline from high school through college and young adulthood. In heterosexual couples, there is no significant difference between the rates of male and female aggressors, unlike in adult relationships.

Does physical aggression decline or increase during high-school, college, and early adulthood?
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A:
decline