In the context of mitigating the impending global warming due to anthropogenic emissions of carbon dioxide, which of the following can be the potential sites for carbon sequestration? 1. Abandoned and uneconomic coal seams 2. Depleted oil and gas reservoirs 3. Subterranean deep saline formations Select the correct answer using the code given below :

The correct answer is (d) because all three are viable geological storage sites: abandoned coal seams adsorb $CO_2$, depleted reservoirs have proven trapping mechanisms, and deep saline formations offer the largest global storage capacity. Option (a) is the most tempting wrong choice for those who doubt the feasibility of saline formations, yet these are scientifically recognized as primary sites for long-term carbon trapping. The core concept being tested is Geological Carbon Sequestration (GCS) as a mitigation strategy for anthropogenic climate change.