If $\mathrm{A}=\left\{1, 2, 3, 4\right\}; \mathrm{B}=\left\{\mathrm{a}, \mathrm{b}\right\}$ and $\mathrm{f}$ is a mapping such that 

$\mathrm{f}: \mathrm{A}\to \mathrm{B}, \mathrm{then} \mathrm{A}\times \mathrm{B}$ is

• A

  $\left\{\left(\mathrm{a}, 1\right), \left(3, \mathrm{b}\right)\right\}$

• B

  $\left\{\left(\mathrm{a}, \right), \left(4, \mathrm{b}\right)\right\}$

• C

  $\left\{\left(1, \mathrm{a}\right), \left(1, \mathrm{b}\right), \left(2, \mathrm{a}\right), \left(2, \mathrm{b}\right), \left(3, \mathrm{a}\right), \left(3, \mathrm{b}\right), \left(4, \mathrm{a}\right), \left(4, \mathrm{b}\right)\right\}$

• D

  None of these