The set of numbers that is always rational is option 3, fractions. Rational numbers are defined as numbers that can be expressed as a ratio of two integers, where the denominator is not zero. Fractions fit this definition as they can be expressed as a ratio of two integers. Integers (option 1) and positive numbers (option 4) can be considered rational, but not always. Decimals (option 2) can be rational or irrational, depending on whether they terminate or have a repeating pattern.
