All natural numbers and $0$ are called the ........ numbers.

### Concept & Logic Number systems are built by progressively expanding sets. The set of **Natural numbers** starts at $1$ ($1, 2, 3...$). When exactly one element, $0$, is added to this set, the resulting collection defines the **Whole numbers**. ### Step-by-Step Solution **Deduction:** 1. Recall the definition of Natural Numbers ($\mathbb{N}$): $\{1, 2, 3, 4, ...\}$ 2. The question asks for the set that combines $\mathbb{N}$ and $\{0\}$. 3. The combined set is $\{0, 1, 2, 3, 4, ...\}$. 4. By mathematical definition, this exact set is known as the Whole Numbers ($\mathbb{W}$). ### Exam Strategy & Shortcut Memorize the hierarchy of basic number systems: Natural (starts at $1$) $\rightarrow$ Whole (adds $0$) $\rightarrow$ Integer (adds negatives). The phrase "and $0$" immediately flags the jump from Natural to Whole. ### Common Pitfall Students frequently confuse "integers" with "whole numbers." Remember that integers also include negative numbers ($-1, -2$), whereas the union of just natural numbers and zero stops exactly at the boundary of whole numbers. ### Final Answer Therefore, the correct answer is **whole**.