Math 6

Question Analysis  
This question assesses operation closure in natural numbers, focusing on subtraction yielding a negative result.
The main focus is to ensure students recognize that subtracting a larger number from a smaller one exits the natural number set.  

Key Concept Explanation  
Natural numbers are positive integers, so subtraction only stays within the set if the result is positive. Negative results (from where ) are not natural numbers.  

Step-by-Step Solution  
1. A. : Natural number. Valid.  
2. B.

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