Hello!
The best way to go through these is to go through each choice.
A. Justin uses irony when he says he has talents:
Irony is defined as something which seems completely different to what is actually true, and thus creates humor. This would be incorrect in this example, as there is nothing regarding whether Justin is actually talented in other aspects, so we don't know whether he's speaking the truth or not.
B. Shawna is not really as smart as Justin thinks:
There is nothing in this play which supports this choice, so thus, this choice would be incorrect.
C. The author uses dramatic irony to create humor:
Dramatic irony is another form of irony. It is obvious to the audience, but not seen by the character(s) in the play. This should be correct as the audience realizes that Justin has made a mistake, however Justin does not know it himself.
D. The audience's knowledge creates sarcasm:
Sarcasm is another form of irony, however, the goal is to mock someone or show contempt. This is incorrect, as the point of this was not to mock Justin, it was to create humor.
I would invite you to draw your own conclusions from the definitions in this case, as I may be wrong.
Hope this helps!
