What defines whether an object is classified as porous, semi-porous, or non-porous?

The classification of an object as porous, semi-porous, or non-porous is fundamentally based on the object's ability to absorb liquids. Porous materials have small openings or pores that allow liquids to enter and be absorbed, making them susceptible to staining and retention of contaminants. Semi-porous materials may absorb some liquid but to a lesser extent than fully porous materials, while non-porous materials do not absorb any liquid at all, making them resistant to staining and easier to clean.

The other options, such as the object's color, material composition, and size, do not directly relate to how liquids interact with the surface of the object. While the material composition can influence the porosity of an object, the key characteristic used to classify the porosity level remains the liquid absorption capability.