Absorption is a common process used in chemical engineering to separate components from a mixture based on their solubility in a solvent. The most common example of absorption is the dissolution of gases in a liquid solvent. Among the given options, option 'A' - Ammonia and air in solvent water - is the most common example of absorption. Let's delve into the details to understand why.

Absorption Process
Absorption is a mass transfer process where a gas or vapor is dissolved in a liquid solvent. It involves the transfer of a solute from a gas phase to a liquid phase. The solute molecules diffuse into the liquid solvent and get trapped within its structure. In the case of gas absorption, the solute molecules are typically dissolved in a liquid solvent.

Ammonia and Air in Solvent Water
Ammonia (NH3) is a common gas that can be absorbed in a liquid solvent. When ammonia gas comes into contact with a liquid solvent like water, it dissolves in the solvent due to the solubility of ammonia in water. This process is commonly observed in various industries where ammonia gas needs to be recovered or removed from a gas stream.

Water as a Solvent
Water is a highly effective solvent for many gases, including ammonia. It has a high affinity for polar molecules and can readily dissolve polar gases like ammonia. The solubility of ammonia in water is influenced by factors such as temperature and pressure. Higher temperatures and lower pressures generally increase the solubility of ammonia in water.

Applications
The absorption of ammonia in water has various applications in industries such as chemical manufacturing, refrigeration, and wastewater treatment. In chemical manufacturing, the absorption of ammonia is used in the production of fertilizers, dyes, and pharmaceuticals. In refrigeration systems, ammonia is absorbed in water to create a refrigerant. In wastewater treatment plants, ammonia is often removed from the wastewater by absorbing it in water.

Conclusion
In conclusion, the most common example of absorption is the dissolution of ammonia gas in water as a solvent. Water has a high solubility for ammonia, making it an effective solvent for this particular gas. The absorption of ammonia in water has various applications in industries such as chemical manufacturing, refrigeration, and wastewater treatment.