Answer: The correct option is (D) {2, 3, 8}
Step-by-step explanation: We are given to find the domain of the following relation :
R : {(3, 5), (8, 6), (2, 1), (8, 6)}.
We know that
if a relation is written in the form of ordered pairs, then the set of first elements of all the ordered pairs form the domain of the relation.
In the given relation, the set of first elements is given by
{2, 3, 8}.
Therefore, the required domain of the given relation is
D = {2, 3, 8}.
Option (D) is CORRECT.