The correct option is A x > y > z
∙ VSEPR theory determines the shape of a molecule based on the repulsions between bond pair-bond pair, bond pair-lone pair and lone pair-lone pair electrons on the central atom.
∙ In a molecule repulsion between electron pairs follow the order:
lone pair - lone pair > lone pair - bond pair > bond pair - bond pair
∙ If a lone pair is present on the central atom, the bond angle decreases because the distance between the lone pair and bond pair electrons increases to minimize repulsions.
∙ If multiple lone pairs are present on the central atom the angle decreases even more due to stronger repulsions.
∙ Therefore bond angle z is least due to the presence of two lone pair followed by y (one lone pair) and x (no lone pairs).