Let $A$ be set of first ten natural numbers and $R$ be a relation on $A$ defined by (x , y) $\in$ $R$ $\Rightarrow$ x + 2y = 10 , then domain of $R$ is

$\begin{aligned} A &=\{1,2,3, \cdots \cdots, 10\} \\ R &=\{(x, y): x+2 y=10, x, y \in A\} \\ & \therefore y=\dfrac{10-x}{2} \\ R &=\{(2,4),(4,3),(6,2),(8,1)\} \\ \therefore & \text { Domain of } R \text { is }\{2,4,6,8\} \end{aligned}$

Correct option is (B).