U2R4 P3:Thirdly, population institutions and specialists can and should play a key role in supporting community organizations, social movements, governments and the international community in improving the nature and form of future urban expansion, and thus enhancing its power to reduce poverty and promote environmental sustainability.第三，人口研究机构和专家能够而且应该发挥关键作用，支持各种社会组织、社会运动、各级政府和国际社会来改进未来城市扩张的性质和形式，从而增强实力，以减少贫困和促进环境的可持续性。The institution should ____________________ (在支持…上起着关键性的作用) social movements and ____________________(提高能力)to reduce poverty.