Answer:
{ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 }
Explanation:
As per the definition, a natural number is a counting number (non-fractional number) that is greater than zero, but not equal to zero.
A set of natural numbers below 12 (but not including 12, because such isn't specified) would henceforth be;
{ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 }