The set of numbers that is always rational is integers.
Rational numbers are defined as numbers that can be expressed as the quotient of two integers (where the denominator is not zero). Since integers can be represented as fractions (for example, an integer \( n \) can be written as \( \frac{n}{1} \)), all integers are rational numbers.
Other options like positive numbers, decimals, and negative numbers can include irrational numbers, so those sets are not guaranteed to be rational.