The relation R={(1, 1), (2, 2), (3, 3)} on the set {1, 2, 3} is :

an equivalence relation

The correct answer is Option (4) → an equivalence relation

(1) Symmetric

for every $a∈\{1,2,3\}$,   $(a,a)∈R$

(2) Reflexive

for $(1, 1), (1, 1)∈R$, $(2, 2), (2, 2)∈R$, $(3, 3), (3, 3)∈R$

(3) Transitive

for every $(a,b),(b,c)∈R$,  $(a,c)∈R$

This is equivalence relation