The correct answer is:
Upset by Utterson persistence.
Mr. Utterson, who´s the main narrator in the novel, has a rational, calm and curious personality. He is a lawyer and consequently a respectable and prosperous man in Victorian London. All these traits, in addition to his persistence, lead him to discover the truth about Dr. Jekyll and Mr. Hyde's relationship.
The correct answer is C. He mistakes Cesario for Sebastian and thinks that Sebastian is refusing to recognize him. It is true that Viola disguised herself as Cesario, but it is Antonio who mistakes him to be Sebastian, and becomes angry at his 'betrayal'
Answer: Cilantro
Explanation: I did it on the i-ready test and got it right