Which agreement rule applies to a subject joined by or nor

What is the best revision of this statement from the body of a cover letter?

What is this scene's impact on the audience? select two options. the verbal irony adds some humor to the scene. the verbal irony shows that brutus is honorable. the verbal irony shows the audience that casca is easily led. the situational irony shows the audience that brutus is honorable. the situational irony shows the audience that casca is not very smart.

What is the italicized part in the sentence , all of the operators are efficient.