In BC13, bond angle = 120$^{\circ}$. In PC13, AsC13 and BiCl3, central atom is $sp^3$ hybridised. Since P, As and Bi are from the same group, bond angle decreases down the group. Hence, overall order of bond angle is : $ \, \, \, \, \, \, \, \, \, $ B > P > As > Bi