After reading the original sentence, we can select the following option when it comes to how the writer should punctuate the nonrestrictive clause to emphasize it:
D) My brother—who is a superb actor—will audition tomorrow for a film role.
With the information above in mind, we can choose letter D as the best option.
The complete question is as follows:
My brother who is a superb actor will audition tomorrow for a film role.
How should the writer punctuate the underlined nonrestrictive clause in order to emphasize it?
A) My brother: who is a superb actor will audition tomorrow for a film role.
B) My brother; who is a superb actor; will audition tomorrow for a film role.
C) My brother who is a superb actor, will audition tomorrow for a film role.
D) My brother—who is a superb actor—will audition tomorrow for a film role.
Learn more about nonrestrictive clauses here:
https://brainly.com/question/977724