Final answer:
The scientific meaning of the term ratio is a comparison of two quantities, such as the mass-to-volume ratio used to define density in substances.
Step-by-step explanation:
The scientific meaning of the term ratio is a comparison of two quantities. In the context of this question, when referring to density, the ratio refers to the mass-to-volume ratio of a substance, which can be represented as mass per unit volume. For example, the density of iron can be calculated if we know that iron has a mass of 23.4 grams and occupies a volume of 3.00 cm³. The density (d) of a substance is indeed an intensive property that provides a measure related to the amount of matter in a given space, defined as the ratio of its mass (m) to its volume (V).
Therefore, the correct answer to the student's question is: a. A comparison of two quantities.