Which of the relations on {0, 1, 2, 3} is an equivalence relation ?

1. A{ (0, 0) (0, 2) (2, 0) (2, 2) (2, 3) (3, 2) (3, 3) }
2. B{ (0, 0) (1, 1) (2, 2) (3, 3) }
3. C{ (0, 0) (0, 1) (0, 2) (1, 0) (1, 1) (1, 2) (2, 0) }
4. D{ (0, 0) (0, 2) (2, 3) (1, 1) (2, 2) }

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Show answer & explanation

Correct answer: B. { (0, 0) (1, 1) (2, 2) (3, 3) }

Explanation

Only the identity relation is reflexive, symmetric and transitive. (A) misses (1,1); (C) misses (2,2); (D) is not symmetric.