Which of the following best describes rational numbers?

Rational numbers are best described as numbers that can be expressed as fractions, where both the numerator and the denominator are integers, and the denominator is not zero. This definition directly supports the correct choice, which states that rational numbers can be expressed as repeating or terminating decimals.

When a rational number is converted to decimal form, it can either terminate after a certain number of digits (like 0.5 or 2.75) or repeat a sequence of digits infinitely (like 1/3, which becomes 0.333...). This property is a defining characteristic of rational numbers, distinguishing them from irrational numbers, which cannot be expressed as such decimals.

On the other hand, options that suggest rational numbers cannot be written as a fraction, include only whole numbers, or are always negative do not align with the definition of rational numbers. Rational numbers encompass a broader range, including positive numbers, negative numbers, and fractions, thus making the selection of option B the most accurate representation of rational numbers.