(a)
Since, $2 + i\sqrt{3}$ is a root of equation $x^{2} + px + q = 0$. Therefore, $2 - i\sqrt{3}$ will be other root.
Now, Sum of the roots $= \left( 2 + i\sqrt{3} \right) + (2 - i\sqrt{3}$ )$= - p$
$\Rightarrow 4 = - p$
Product of roots $= \left( 2 + i\sqrt{3} \right) + (2 - i\sqrt{3}) = q$
$\Rightarrow 7 = q$
Hence, $(p,q) = ( - 4,\ 7)$