It's impossible to definitively say what the "most common" solvent acting on surfaces is because it depends heavily on the context. Here's why:

* Context is key: "Most common" could refer to:

* Natural environments: In this case, water would be the most common solvent. It's ubiquitous and plays a major role in weathering and erosion.

* Industrial applications: Here, solvents like acetone, ethanol, and toluene are prevalent in cleaning, degreasing, and paint thinning.

* Specific materials: Different materials react differently to solvents. For example, hydrocarbons are used for dissolving fats and oils, while polar solvents like water are better for dissolving salts.

* Scale matters: The "most common" solvent could change depending on whether we're talking about the macroscopic world (e.g., cleaning a countertop) or the microscopic level (e.g., interactions within a cell).

Therefore, to determine the most common solvent, you need to specify the context.

Here are some examples:

* Most common solvent for cleaning household surfaces: Water, with detergents or soaps.

* Most common solvent in the chemical industry: Acetone, for its versatility and low cost.

* Most common solvent for dissolving biological molecules: Water, due to its polar nature.

Let me know if you have a specific context in mind, and I can give you a more precise answer.