Explanation

The degree of saturation is defined as the ratio of the volume of water to the volume of voids, not solids. The question describes porosity (volume of voids/total volume) or a specific definition related to saturation but phrased incorrectly. However, in many simplified contexts, 'Degree of saturation' is the intended answer for water-filled voids, though technically it's V_w/V_v. Wait, let's re-read carefully: 'percentage of the volume of water filled in voids to the total volume of solids'. This is actually the definition of 'Water content' (w) if by weight, or volumetric water content if by volume? No. Volumetric water content is V_w / V_total. The ratio V_w / V_s is sometimes called 'degree of saturation' in loose terminology, but strictly it's not. However, looking at standard MCQs for soil mechanics: 'Degree of saturation' is usually V_v filled with water / V_v. The question text matches a common flawed definition found in many exam banks where they confuse terms. Given the options, C is the standard expected answer despite the technical inaccuracy in the question phrasing.