On graduation day, Jon walked across the auditorium stage, proud of what he (accomplished) choose the correct form of the verb in parentheses A. Had accomplished B. Accomplished C. Accomplish D. Accomplishes

The answer I think is right is C. Accomplished

The correct form of the form that should be used to replace the one in the parentheses would be option A. Had accomplished. This tense of the verb is called the past perfect tense. We used the past perfect tense because the action mentioned in this sentence has been completed in the past.