Numerical answer
The four sentences below, when properly sequenced, form a coherent paragraph. Decide the correct order and key in the sequence (e.g., 3142) as your answer.
1. Because groundwater moves slowly, often only metres per year, pollutants introduced decades ago can still be migrating toward wells that have not yet detected any contamination.
2. This delay complicates efforts to link a specific industrial or agricultural practice to a later contamination event, since the responsible activity may have ended long before its effects become visible.
3. Unlike surface water, which can flush a contaminant downstream within days, groundwater carries pollution forward on a timescale poorly matched to ordinary regulatory or political attention spans.
4. Recognising this mismatch is essential for any policy that hopes to prevent, rather than merely react to, groundwater contamination.
1. Because groundwater moves slowly, often only metres per year, pollutants introduced decades ago can still be migrating toward wells that have not yet detected any contamination.
2. This delay complicates efforts to link a specific industrial or agricultural practice to a later contamination event, since the responsible activity may have ended long before its effects become visible.
3. Unlike surface water, which can flush a contaminant downstream within days, groundwater carries pollution forward on a timescale poorly matched to ordinary regulatory or political attention spans.
4. Recognising this mismatch is essential for any policy that hopes to prevent, rather than merely react to, groundwater contamination.
Show answer and solution
Answer: 3124
Sentence 3 sets up the contrast between fast-flushing surface water and slow-moving groundwater, introducing the core idea of mismatched timescales. Sentence 1 elaborates on why groundwater is slow, explaining the mechanism (metres per year) and its consequence (undetected migrating pollutants). Sentence 2 extends this into a practical complication (linking cause to effect across a long delay). Sentence 4 closes with the policy implication, which depends on the mismatch already being established. Order: 3-1-2-4.
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