Understanding Problems Associated with Burning Coal

Burning coal is a major source of energy production globally, but it comes with significant environmental and health problems. Let's examine the issues mentioned in the options:

• Carbon-dioxide emission: Coal combustion releases large amounts of carbon dioxide (\(\text{CO}_2\)). Carbon dioxide is a primary greenhouse gas that contributes to global warming and climate change by trapping heat in the Earth's atmosphere. This is a well-documented problem associated with burning coal.
• Acid rain: Burning coal releases pollutants like sulfur dioxide (\(\text{SO}_2\)) and nitrogen oxides (\(\text{NO}_x\)) into the atmosphere. These gases react with water, oxygen, and other chemicals to form sulfuric and nitric acids. These acids then fall to the ground as acid rain, which can damage forests, lakes, buildings, and infrastructure, and harm aquatic life. Acid rain is a direct consequence of emissions from coal-fired power plants.
• Ash with toxic metal impurity: The combustion of coal produces large quantities of solid waste material, including fly ash and bottom ash. This ash often contains various toxic heavy metals such as mercury, lead, arsenic, and chromium, which were present as impurities in the original coal. Improper disposal of this ash can contaminate soil and water resources, posing risks to human health and ecosystems.

Based on the analysis of each option:

• Carbon-dioxide emission is a significant problem.
• Acid rain caused by coal emissions is a significant problem.
• Toxic ash containing heavy metals is a significant problem.

Since all three listed problems are associated with the burning of coal, the most appropriate answer is that all of them are problems.