An "adaptation" is, by dictionary definition, "a movie, television drama, or stage play that has been adapted from a written work, typically a novel." Answer C, "a musical based on the life of a popular band," meets the definition of an adaptation.
The appearance of Tybalt foreshadows Romeo's eventual death as he narrowly escapes it at Tybalt's hands. It creates a sense of impending danger for Benvolio, Mercutio and the audience as it is the first indication that Romeo is doomed.
