Which numbers are defined as natural numbers?

Natural numbers are defined as the set of positive integers that are used for counting. This means they start from 1 and continue indefinitely: 1, 2, 3, 4, and so on. This set does not include any negative numbers, fractions, or decimals.

The option that lists the numbers starting from 1 and continuing onward accurately reflects this definition, making it the correct choice. While some contexts include 0 in the set of natural numbers, the most widely accepted definition in arithmetic focuses solely on positive integers.

In contrast, the other options include numbers that do not fit the criteria for natural numbers. The inclusion of zero or negative numbers moves those options outside the standard definition of natural numbers. Thus, the correct answer represents the core concept of natural numbers as used in mathematics.