Abiotic factors are non-living chemical and physical components of the environment that affect living organisms and the functioning of ecosystems. Examples that represent abiotic factors affecting biotic factors from your list include:
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Sediment builds up in a riverbed, slowing the river’s speed. - This affects the ecosystem and can impact organisms living in the river.
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Ash from a volcanic eruption kills new plant growth. - The ash is an abiotic factor, and its presence can directly affect plant life.
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Warm water from a nuclear power plant causes overgrowth of algae. - The temperature of the water is an abiotic factor that can influence algal growth.
The other options do not represent abiotic factors affecting biotic factors:
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A hungry raccoon consumes a freshwater clam. - This example describes a biotic interaction (predation) and does not illustrate the influence of abiotic factors.
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A river floods and deposits tree pollen along its banks. - While flooding is an abiotic factor, the deposition of pollen itself is not; it describes a reproductive process of plants.
Thus, the correct examples are the first three: sediment buildup, volcanic ash, and warm water from a nuclear power plant.