Final answer:
The missing step in the given proof is to state that angles ���acb and ���oca are congruent.
Step-by-step explanation:
In the given proof, the missing step is to state that angles ���acb and ���oca are congruent. This is because angles ���acb and ���pcq are corresponding angles formed by the parallel lines cut by a transversal. Similarly, angles ���ocp and ���abc are also corresponding angles formed by the parallel lines cut by a transversal.