Read the passage below and match each scholarly viewpoint (Left Column) with its specific structural role in the overall development of the passage's argument (Right Column).
Passage:
For decades, historical consensus attributed the decline of the Indus Valley civilization around 1900 BCE to violent external conquest, a hypothesis anchored in early twentieth-century excavations that uncovered unburied skeletons in the upper strata of Mohenjo-daro. However, mid-twentieth-century environmental geologists challenged this catastrophic invasion model, contending instead that tectonic activity altered the course of major river systems like the Ghaggar-Hakra, precipitating acute agricultural failure and sudden city abandonment. Most recently, contemporary climate scientists and bioarchaeologists have dismissed both single-cause paradigms in favor of a nuanced, multi-causal framework. Utilizing high-resolution paleoclimate proxies, these researchers demonstrate that a centuries-long weakening of the summer monsoon forced a gradual retreat from massive urban centers toward rural agricultural settlements. Far from an abrupt collapse driven by conquest or seismic shift, the transition represents a decentralizing adaptation to shifting ecological realities, during which trade networks reoriented rather than vanished entirely.
- The early 20th-century invasion hypothesisIntroduced as the traditional consensus to establish a baseline view that the passage subsequently shows was reliant on flawed structural assumptions.
- The mid-20th-century hydro-geological modelServes as an intermediate structural pivot that shifted analytical focus to environmental factors, though still limited by a single-cause framework.
- The contemporary paleoclimate frameworkRepresents the ultimate synthesis endorsed by the passage, reframing the civilization's end from a sudden catastrophic collapse to a gradual adaptive transition.