Ans is B
Mathematical Relations
Given sets D1, D2, …, Dn, not necessarily distinct.
The Cartesian product D1xD2x…xDn is the set of all (ordered) n-tuples such that d1∈D1, d2 ∈ D2, …, dn ∈ Dn
A mathematical relation on D1, D2, …, Dn is a subset of the Cartesian product D1xD2x…xDn. ƒ D1, D2, …, Dn are the domains of the relation.
n is the degree of the relation.
The number of n-tuples in a given relation is the cardinality of that relation; the cardinality of a relation is always finite.