(i) The low oxidation state of phosphorus
(ii) Presence of two –OH groups and one P–H bond
(iii) Presence of one –OH group and two P–H bonds
(iv) High electron gain enthalpy of phosphorus
Correct Answer: (iii) Presence of one –OH group and two P–H bonds
Explanation: Strong reducing behaviour of H3PO2 is due to the presence of one –OH group and two P–H bonds.