Math 6

Question Analysis  
This question involves arithmetic operations on natural numbers, focusing on identifying which operation yields a non-natural number.
The main focus is to test the closure properties of natural numbers under addition, multiplication, subtraction, and division, especially with larger values.  

Key Concept Explanation  
Natural numbers: Positive integers ≥1, closed under addition and multiplication (results are always natural numbers). 
Subtraction: Not closed—if the subtrahend exceeds the minuend, the result is negative (not a natural number).  
Division: Not closed—may yield non-integers (e.g., fractions/decimals) unless exact.  

Step-by-Step Solution  
1. A. : Sum of natural numbers is a natural number. Valid.  
2. B.