Why is there a concern about copper smelting plants? 1. They may release lethal quantities of carbon monoxide into environment. 2. The copper slag can cause the leaching of some heavy metals into environment. 3. They may release sulphur dioxide as a pollutant. Select the correct answer using the code given below.

- Copper smelting often involves processing sulfide ores, leading to the release of large quantities of sulfur dioxide (SO2), a major air pollutant causing acid rain and respiratory issues. Statement 3 is correct. - Copper slag, a waste byproduct of the smelting process, contains various heavy metals (including copper, lead, zinc, arsenic, etc.). There is a significant concern about the leaching of these heavy metals into the environment, contaminating soil and water. Statement 2 is correct. - While carbon monoxide (CO) is a toxic gas produced from incomplete combustion processes which might occur in some parts of smelting, it is not typically highlighted as the primary or most widespread lethal air pollution concern from large-scale copper smelting operations compared to SO2. Statement 1 is less likely to be a major defining concern.