Final answer:
The missing reasons in the proof involve using the given bisections to apply the Angle-Side-Angle congruence criterion, demonstrating that triangles PMO and NMO are congruent.
Step-by-step explanation:
The question is regarding a geometric proof for the congruence of two triangles based on given bisecting lines.
To complete the two-column proof, you would use the given information that MO bisects ∠PMN and OM bisects ∠PON, which implies that ∠PMO = ∠NMO and ∠MOP = ∠MON.
By the Reflexive Property, we also know that segment OM is equal to itself. Hence, by the Angle-Side-Angle (ASA) congruence criterion, we can conclude that △PMO ≅ △NMO.