Assertion–Reason (North Indian rivers flood in summer) Assertion (A): Most rivers in the North Indian plains experience flooding during the summer season. Reason (R1): Many rivers originate in the Himalayas and are fed by melting snow. Reason (R2): The rivers are also fed by monsoon rains during the summer months. Identify which reason(s) truly explain A.
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AIf only reason 1 (R1) and not reason 2 (R2) is the reason for the assertion (A).
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BIf only reason 2 (R2) and not reason 1 (R1) is the reason for the assertion (A).
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CIf both (R1) and (R2) are reasons for the assertion (A).
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DIf neither (R1) nor (R2) is the reason for the assertion (A).
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ENone of these
Answer
Correct Answer: If both (R1) and (R2) are reasons for the assertion (A).
Explanation
Introduction / Context:Flood seasonality in North Indian plains reflects dual inputs: Himalayan snowmelt and monsoon rainfall. The item asks if both reasons explain observed summer flooding.
Given Data / Assumptions:
- A: Summer flooding is common.
- R1: Snowmelt augments discharge from Himalayan catchments.
- R2: Monsoon rains peak in summer, further increasing flows.
Concept / Approach:Hydrographs in snow–monsoon regimes show combined contributions. When both inputs overlap temporally, peak flows and flood probability rise.
Step-by-Step Solution:
1) R1 adds sustained baseflow and diurnal melt pulses.2) R2 adds intense rainfall-runoff, sometimes overwhelming river capacity.3) Superposition of inputs explains seasonal floods—thus both reasons are valid.Verification / Alternative check:Historical flood records align with monsoon onset and elevated melt periods.
Why Other Options Are Wrong:A/B understate the dual-driver nature; D contradicts hydrology.
Common Pitfalls:Treating snowmelt and monsoon as mutually exclusive.
Final Answer:If both (R1) and (R2) are reasons for the assertion (A).