Detailed Explanation:

Answer: Option 4 — 1, 2 and 3

All three options represent viable geological sites for carbon sequestration, which is the process of capturing and storing atmospheric carbon dioxide to mitigate global warming. These geological formations possess the necessary characteristics—porosity, permeability, and secure cap rocks—to safely store CO₂ underground for extended periods.

✅ Statement 1 – Correct: Abandoned and uneconomic coal seams can store CO₂ through a process called coal seam carbon sequestration, where CO₂ is adsorbed onto the coal matrix, potentially displacing methane in the process.

✅ Statement 2 – Correct: Depleted oil and gas reservoirs are proven storage sites as they have already trapped hydrocarbons for millions of years, indicating their capacity to securely contain injected CO₂ with existing infrastructure.

✅ Statement 3 – Correct: Subterranean deep saline formations (aquifers) are among the most promising and abundant carbon storage sites globally, offering vast storage capacity far below freshwater resources with minimal environmental risk.