# The volume in ml. of 0.1 M solution of NaOH required to completely neutralize 100 ml. of 0.3 M solution of $H_3PO_3$ is :

$\begin {array} {1 1} (1)\;60 & \quad (2)\;600 \\ (3)\;300 & \quad (4)\;30 \end {array}$

(2) 600