The number that fits into all the specified sets—natural numbers, whole numbers, and integers—is 12.
Here's the reasoning:
- Natural numbers are the positive integers (1, 2, 3, ...), and 12 is a natural number.
- Whole numbers include all natural numbers and zero (0, 1, 2, 3, ...), and 12 is also a whole number.
- Integers include all whole numbers and their negative counterparts (..., -3, -2, -1, 0, 1, 2, 3, ...), so 12 is also an integer.
The other options do not fit into all three categories.