If (R) is symmetric and contains ((a,b)) where (a\ne b), which minimum pair must also be present to maintain symmetry?

Correct answer: ((b,a))

Step 1: When (a\ne b), the reverse of ((a,b)) is a different pair ((b,a)). Step 2: This reverse pair is required for symmetry. Step 3: For non-diagonal pairs, do not forget to write the reverse separately.