Answer:

Introduction:
Comparing two quantities is a fundamental concept in mathematics. It helps us understand the relationship between two values and make meaningful comparisons. One way to compare two quantities is through the use of ratios.

Ratio:
A ratio is a comparison of two numbers or quantities. It expresses the relative size or amount of one quantity in relation to another. Ratios can be written in different forms, such as using a colon (:) or as a fraction. For example, if we have 3 apples and 4 oranges, the ratio of apples to oranges can be written as 3:4 or 3/4.

Comparison:
Comparing two quantities using a ratio involves determining the relationship between them. This can be done by dividing one quantity by the other. The resulting quotient represents the ratio between the two quantities. For example, if we want to compare the heights of two buildings, we can measure their heights and calculate the ratio by dividing one height by the other.

Example:
Let's say we have two buildings, A and B, with heights of 60 meters and 45 meters respectively. To compare the heights of the two buildings, we can calculate the ratio of their heights:

Ratio = Height of A / Height of B
= 60 / 45
= 4/3

This means that building A is 4/3 times taller than building B.

Conclusion:
In conclusion, comparing two quantities involves determining their ratio, which expresses the relative size or amount of one quantity in relation to another. Ratios provide a way to make meaningful comparisons and understand the relationship between different quantities. Therefore, option A, "Ratio," is the correct answer for the given question.