The audience knows that Romeo can hear Juliet, but she doesn't know this.
This is an example of D. Dramatic Irony.
This is because dramatic irony is when the reader, viewer, or audience knows something that the character in a story does not.
Hope this helps! :)
Drama is defined as a story told in action by actors impersonating the characters of the story would be considered as to being true.
Here is a picture of what I answered (I had this question on a test)