Concept:The verb "discuss" is transitive, so it takes a direct object without any preposition.Explanation:The correct structure is "discuss something," not "discuss about something" or "discuss on something."Using "about" or "on" after "discuss" is redundant and grammatically incorrect.The sentence refers to the teachers’ action in the past, so the past continuous tense "were discussing" is appropriate.Thus, the only correct option is "were discussing," as it uses the transitive verb correctly with the object "our poor performance."Answer:D. were discussing