Correct Answer - Option 2 : D
1 × D
2 × ...× D
n
The correct answer is "option 2".
CONCEPT:
Given a set of domains D1, D2,..., Dn,
The Cartesian product D1 X D2 x...x Dn is set of all n-tuples(ordered) <d1,d2...dn> such that d1 ∈ D1, d2 ∈ D2, …, dn ∈ Dn.
So, the Mathematical relation on D1, D2,..., Dn is a subset of Cartesian product D1 X D2 x...x Dn.
Hence, the correct answer is "option 2".