How did the Harappan civilization come to an end? A. It appears as if the…

Concept: Historians treat the collapse of an ancient urban civilization as the outcome of several compounding stresses, not one single event; a proposed cause is accepted into the standard explanation only when the available evidence supports it at the scale being claimed for it -- a change documented at a handful of excavated sites cannot be generalized into an event that struck the entire civilization.

Application: The Harappan civilization spanned a very large area, from Sindh and Baluchistan across Gujarat, Rajasthan, Punjab and Haryana, and went into decline from around 1900 BCE. Because the Harappan script remains undeciphered, historians have no direct textual record of the decline and can only reconstruct it from excavated site data and environmental proxies. The explanation officially recognized in the exam key combines three factors commonly proposed by historians: weakening administrative and trade control over the cities, large-scale deforestation for fuel, brick-firing and construction (which some researchers link to soil degradation and reduced rainfall), and the drying up or course-shifting of major rivers such as the Ghaggar-Hakra system, undermining agriculture and settlement viability. Taken together, these three factors form the commonly cited multi-causal account -- not an independently proven single cause, but the officially keyed combination that best matches the available evidence.

• A, B, C -- Harappan settlements stretched across a huge and environmentally varied region, from the marshy Indus delta to the drier tracts of Rajasthan and Gujarat. A single flood large enough to have struck this entire span at once has no supporting stratigraphic record outside a few excavated mounds, so reading this combination's flood claim as civilization-wide goes beyond the geographic reach the excavations actually cover.

• A, C, D -- The excavated evidence for flooding takes the form of localized silt deposits found at only a handful of individual mounds. Treating that kind of site-level clue as proof of a flood spanning the whole civilization conflates a narrow stratigraphic observation with a sweeping historical claim about the entire region.

• B, C, D -- A flood implies a single, comparatively sudden calamity, whereas the broader decline is understood to have unfolded gradually over generations. Assuming one dramatic, civilization-wide flood drove the collapse conflates that slow, multi-generational process with a single sudden catastrophe.

Result: Because only the combination of rulers losing control, deforestation, and rivers drying up avoids over-generalizing the localized flood evidence to the whole civilization, A, B, D is the officially keyed explanation -- confirmed by the CTET December 2019 Paper 2 answer key (Q50), which records this combination as correct.