Final answer:
Ballet achieved its modern identity in the 19th century through significant changes in technique, style, and structure. The correct option is d.
Step-by-step explanation:
The art form of ballet achieved its modern identity in the 19th century. During this time, significant changes occurred in both the technique and style of ballet, transforming it into the form that is recognized today.
One crucial development in the 19th century was the establishment of ballet as a standalone art form rather than a subsidiary of other theatrical productions. Choreographers such as Marius Petipa and composers like pyotr tchaikov sky played essential roles in shaping ballet during this period.
By the 19th century, ballet had undergone significant changes in technique, costuming, and narrative structure, which eventually led to the development of the classical ballet vocabulary that is still practiced today. The correct option is d.