Answer:
A. ensemble.
Step-by-step explanation:
A musical ensemble can be defined as a group of people who play instrumental and vocal music. It is also known as a music group and carries a distinct name. The word ensemble is derived from the Middle French ensemblée, meaning together at the same time.
A rock band will come under the category of a musical ensemble as it is also a group of people performing instrumental music or vocal music.
Therefore, option A is correct.