单选题 .  ①Recent studies of ancient Maya water management have found that the urban architecture of some cities was used to divert rainfall runoff into gravity-fed systems of interconnected reservoirs. ②In the central and southern May Lowlands, this kind of water control was necessary to support large populations throughout the year due to the scarcity of perennial surface water and the seasonal availability of rainfall. ③Some scholars argue that the concentration of water within the urban core of these sites provided a centralized source of political authority for Maya elites based largely on controlled water access. ④Such an argument is plausible; however, it is less useful for understanding the sociopolitical implications of water use and control in other, water-rich parts of the Maya region.47.  The author of the passage implies which of the following about the political importance of the type of urban water management system described in the passage? ______