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 ****D**_{1 }X D2 x...x Dn is** set** of all **n-tuples**(ordered) **<d**_{1},d_{2}...d_{n}> such that **d**_{1} ∈ D1, d2 ∈ D2, …, d_{n} ∈ D_{n}_{.}

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".**