Passage two Questions 51 to 55 are based on the following passage Twenty years ago, the urban land institute defined the two types of cities that dominated the us landscape: smaller cities that operated around standard 9-5 business hours and large metropolitan areas that ran all 24 hours of the day. analyzing and comparing cities using the lens of this basic divide gives interesting context to how investment capital flows and housing prices have In recent years, many mid-sized cities have begun to adopt a middle-of-the-road approach incorporating the excitement and opportunity of large cities with small cities' quiet after midnight.these18-hour cities are beginning to make waves in real estate rankings and attract more reaestate investment. what is underlying this new movement in real estate, and why do these cities have so much appeal 18-hour cities combine the best of 24-hour and 9-5 cities, which contributes to downtown revitalization. for decades, many downtown cores in small to mid-sized cities were abandoned after work hours by workers who lived in the suburbs. movement out of city centers was widespread and downtown tenants were predominantly made up of the working poor. this generated little ommerce for downtown businesses in the evenings, which made business and generating tax renenue for municipal upkeep difficult. with the rise of a new concept in urban planning that aims and more conver increasing popularity for urban areas treal estate pushes in major cities like san francisco or new york, has inspired a type of forward thinking urbanity and in smaller cities Transforming downtown areas so that they incorporate modern housing and improved walkability to local restaurants, retail and entertainment -especially when combined with improved infra structure for cyclists and public transit-makes them appeal to a more affluent demographic. these adjustments encourage employers in the knowledge and talent industries to keep their offices downtown. access to foot traffic and proximity to transit allow the type of entertainment-oriented businesses such as bars and restaurants to stay open later, which attracts both younger, creative workers and baby boomers nearing retirement alike. because of their smaller size, most keep hours that allow people to enjoy themselves, then have some quiet after midnight, as opposed to large ajor cities like new york, where the buzz of activity is ongoing. These 18-hour cities are rapidly on the rise and offer great opportunities for ho investment in many of these cities such as denver, a diverse and vigorous economy attracted to the urban core has offered stable employment for residents. the right urban mix has propped up home occupancy increased property values, and attracted significant investment capital. what do we learn about american cities twenty years ago？A.they were divided into residential and business areas
B.their housing prices were linked with their prosperity.
C.there was a clear divide between large and small cities
D.they were places where large investment capital flowed.
what can be inferred from the passage about 18-hour cities？A.they especially appeal to small businesses
B.they have seen a rise in property prices.
C.they have replaced quiet with excitement
D.they have changed america's landscape
what characterizes the new downtown areas in 18-hour cities？A.a sudden emergence of the knowledge industry.
B.flooding in of large crowds of migrant workers
C.housing and improved infrastructure
D.more comfortable life and greater upward mobility.
what have 18-hour cities brought to the local residents？A.more chances for promotion.
B.greater cultural diversity.
C.healthier living environment.
D.Better job opportunities
53 years ago, many downtown cores in small to mid-sized cities().A.had hardly any business activity
B.exhibited no signs of prosperity
C.were crowded in business hours
D.looked deserted in the evenings
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Using GRAPH-SEARCH, when a node is expanded it is added to the closed set. This means that even if a node is added to the fringe multiple times it will not be expanded more than once. Consider an alternative version of GRAPH-SEARCH, LOOKAHEAD-GRAPH-SEARCH, which saves memory by using a "fringe-closed-set" keeping track of which states have been on the fringe and only adding a child node to the fringe if the state of that child node has not been added to it at some point. Concretely, we replace the highlighted block above with the highlighted block below.
Now, we've produced a more memory efficient graph search algorithm. However, in doing so, we might have affected some properties of the algorithm. To explore the possible differences, consider the example graph below.
Q13.1 If using LOOKAHEAD-GRAPH-SEARCH with an A* node expansion strategy, which path will this algorithm return? (We strongly encourage you to step through the execution of the algorithm on a scratch sheet of paper and keep track of the fringe and the search tree as nodes get added to the fringe.)
