#### Answer

$\text{1) whole number, } \text{2) integer, } \text{3) rational number, } \text{4) real number} $

#### Work Step by Step

$\bf{\text{Solution Outline:}}$
Use the definitions of the different classification of numbers.
$\bf{\text{Solution Details:}}$
Natural numbers are the numbers $\{1,2,3,...\}$.
Whole numbers are the numbers $\{0,1,2,3,...\}$.
Integers are the numbers $\{...,-3,-2,-1, 0,1,2,3,...\}.$
Rational numbers are numbers that can be expressed as the ratio between $2$ integers.
Irrational numbers are numbers that CANNOT be expressed as the ratio between $2$ integers.
Real numbers are the combined numbers in the set of rational and irrational numbers.
The given number, $ 0 ,$ is classified as \begin{array}{l}\require{cancel}
\text{1) whole number, } \text{2) integer, } \text{3) rational number, } \text{4) real number} .\end{array}