Baltes et al.'s research in gerontology is focused on plasticity. the research uses the term "plasticity" to describe people's capacity. plasticity refers to the belief that capacity is not fixed but can be learned or improved with practice. which core issue of human development does baltes et al.'s research explore? a. stability–change issue b. universal versus context-specific controversy c. continuity–discontinuity controversy d. nature–nurture issue

Urban growth invariably feeds increased commercialization and industrialization. it requires continually expanding land areas. when urbanization rates are high, and countries do not have the institutional and managerial capacities or economic wherewithal to manage such rapid growths, they exert intense pressure on the types and nature of the resulting settlements. they contribute to the development of overcrowded slums and shanty towns without adequate essential services and necessary infrastructure.-by asit k. biswas and cecilia tortajada