Math 6

Question Analysis
This question involves multiple concepts related to natural numbers, including their range, arithmetic properties, and closure properties.
The main focus is to comprehensively test students' understanding of the fundamental characteristics of natural numbers.

Key Concept Explanation
Natural numbers are positive integers starting from 1.
They are closed under multiplication (the product of two natural numbers is always a natural number), but not closed under subtraction (the difference between two natural numbers can be 0 or a negative number, which are not natural numbers).

Step-by-Step Solution
Option A is incorrect because the smallest natural number is 1, not 0. 0 is part of the set of whole numbers but not natural numbers.
Option B is incorrect as natural numbers are only positive integers and do not include negative integers.
Option D is incorrect because if and are natural numbers, is always a natural number, so natural numbers are closed under multiplication.
Option C is correct because, for example, if