If z₁, z₂ and z₃, z₄ are two pairs of conjugate complex numbers, then $\arg \left(\frac{z_1}{z_4}\right)+\arg \left(\frac{z_2}{z_3}\right)$ equal 

$\arg \left(\frac{z_1}{z_4}\right)+\arg \left(\frac{z_2}{z_3}\right)$ 

  $=\arg \left(\frac{z_1{z}_2}{z_4{z}_3}\right)+2k\pi =\arg \left(\frac{{\left|z_1\right|}^2}{{\left|z_3\right|}^2}\right)+2k\pi =2k\pi$

where k = 0 or 1

  [ $z_1= z_3 = i,$ gives answer 2p and $z_1 = z_{3 }= 1$, gives answer 0]