Which type of number includes a decimal portion?

The correct choice is real numbers because this category encompasses all rational and irrational numbers, including those with decimal portions. Real numbers can be positive, negative, or zero, and they cover any number that can be expressed on the number line, which includes decimals.

In contrast, whole numbers refer to non-negative numbers without any fractions or decimals, starting from zero and including 1, 2, 3, etc. Integer numbers also do not include decimal portions; they encompass whole numbers and their negative counterparts, such as -1, 0, 1, 2, etc. Natural numbers are the set of positive integers starting from 1 (or sometimes 0) and do not include any decimal or fractional parts either.

Thus, the definition of real numbers clearly includes the possibility of decimal components, making it the accurate answer.