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If R is a relation on A={a,b,c}A = \{a, b, c\} such that R={(a,a),(b,b)}R = \{(a,a), (b,b)\}, which element/elements should be included to make R an equivalence relation.

A. (c, c)

B. (c, c), (a, c), (c, a)

C. (a, b), (b, c), (a, c)

D. (b, c), (c, c), (c, a), (b, a)

Choose the correct answer from the options given below:

Solution

✅ Correct Option: 3

For equivalence: reflexive, symmetric, transitive.

A: Adding (c,c)(c,c) gives {(a,a),(b,b),(c,c)}\{(a,a),(b,b),(c,c)\} - reflexive, symmetric, transitive. Valid.

B: Adding (c,c),(a,c),(c,a)(c,c),(a,c),(c,a) - reflexive, symmetric ((a,c),(c,a)(a,c),(c,a) both present), transitive (all required pairs exist). Valid.

C and D introduce pairs without their symmetric/transitive closures, so they fail.

Hence A and B only.

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