Dust levels are controlled by spraying roads and stockpiles, and water pollution is controlled by carefully separating clean water runoff from runoff which contains sediments or salt from mine workings. The latter is treated and reused for dust suppression. Noise is controlled by modifying equipment and by using insulation and sound enclosures around machinery.
To control dust at mine sites, mining companies often use
Result:
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Option 2: "Runoff water containing sediments."
Explanation: This option is correct as the text states that water containing sediments from mine workings is treated and reused for dust suppression. This directly supports the answer, as it highlights the method used by mining companies to control dust at mine sites.
Option 1: "Freshwater from nearby dams."
Explanation: This option is incorrect because the text does not mention the use of freshwater from dams for dust control. Instead, it specifies that water pollution is managed by separating clean water runoff from contaminated runoff, which indicates that freshwater is not the primary source for dust suppression.
Option 3: "Topsoil taken from the site before mining."
Explanation: This option is incorrect because the text does not mention the use of topsoil for dust control. Instead, it focuses on the treatment and reuse of runoff water containing sediments, making this option irrelevant to the context of dust control.
Option 4: "Chemicals that may be toxic."
Explanation: This option is incorrect as the text explicitly states that coal mining produces no toxic chemical wastes. Therefore, the use of potentially toxic chemicals for dust control contradicts the information provided in the text.
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