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A lake near a village suffered heavy fish mortality. What were the two main causes?(a) High urea and phosphate fertilizer runoff from nearby crops.(b) Area was sprayed with .(c) The lake water turned green and stinky.(d) Phytoplankton population declined initially.

  1. A
    a, b
  2. B
    b, c
  3. C
    c, d
  4. D
    a, c

Solution & Step-by-step Explanation

Runoff of fertilizers (urea/phosphates) leads to eutrophication (a). This causes massive algal blooms, making the water green and stinky (c). As the algae die and decompose, dissolved oxygen is depleted, leading to the death of fish.

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A lake near a village suffered heavy fish mortality. What were the two main causes?(a) High urea and phosphate fertilizer runoff from nearby crops.(b) Area was sprayed with .(c) The lake water turned green and stinky.(d) Phytoplankton population declined initially.
A
a, b
B
b, c
C
c, d
D
a, c

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Environmental IssuesWater PollutionEutrophication

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