Explanation:

Density ($\rho$) is a fundamental physical property of matter that expresses the relationship between the mass of a substance and the volume it occupies. It is defined as the mass per unit volume. Mathematically, this relationship is expressed as: $$\rho = \frac{\text{Mass}}{\text{Volume}}$$ Option A ($ \text{Mass} \times \text{Volume} $) would yield a product, not a ratio, and does not represent density. Option B ($ \text{Volume} / \text{Mass} $) represents the reciprocal of density, often called specific volume. Option C ($ \text{Mass} + \text{Volume} $) is a sum of two different physical quantities and has no physical meaning as density. Therefore, the correct definition is Mass divided by Volume.