Concept:The “good commander” is the military leader whom Cassio has disappointed through his drunken misconduct.Explanation:Cassio is the speaker in this extract, lamenting that his drunken behaviour has shamed him before his general.That general is Othello, who appointed Cassio as his lieutenant.Thus, the phrase “so good a commander” clearly refers to Othello.Answer:C. Othelo (Othello)