The relation R defined on the set of natural numbers as $\left\{\left(\mathrm{a}, \mathrm{b}\right): \mathrm{a} \mathrm{differs} \mathrm{from} \mathrm{b} \mathrm{by} 3\right\},$ is given by

• A

  $\left\{\left(1, 4\right), \left(2, 5\right), \left(3, 6\right)......\right\}$

• B

  $\left\{\left(4, 1\right), \left(5, 2\right), \left(6, 3\right)......\right\}$

• C

  $\left\{\left(1, 3\right), \left(2, 6\right), \left(3, 9\right)......\right\}$

• D

  None of these