Final answer:
The markings on a standard ruler include both whole numbers and fractions, which collectively form the set of rational numbers. So, the correct option is C) Rational numbers.
Explanation:
The markings on a standard ruler encompass whole numbers, fractions, and decimals, thus representing a combination of integers and fractions. Integers consist of whole numbers and their additive inverses, including zero and negative whole numbers. Rational numbers, on the other hand, encompass integers as well as fractions, which can be expressed as a ratio of two integers. The markings on a ruler denote measurements that could be in fractional form, like 1/2 inch, 1/4 inch, or even smaller denominations such as 1/8 inch or 1/16 inch.
Moreover, rational numbers include terminating and repeating decimals, all of which are encompassed within the markings on a standard ruler. Even though the ruler might not explicitly display decimal fractions, the divisions between whole numbers can represent infinite fractions. Each marking on the ruler corresponds to a specific measurement, which, when expressed as a decimal, can potentially be infinite in its decimal expansion, thus falling under the realm of rational numbers.
In essence, the ruler markings cover a spectrum of numerical representations, from whole numbers to fractions, and even though not all fractions or decimals might be visibly marked, their inclusion is implicit within the range of measurements denoted on the ruler. Therefore, the set of numbers that best describes the markings on a standard ruler is the set of rational numbers.
So, the correct option is C) Rational numbers.