Final answer:
Carlo Blasis was a significant ballet teacher and theorist, not an opera singer, composer, or conductor. His contributions to ballet technique and education have had a lasting impact on the field.
Step-by-step explanation:
The individual mentioned in the student's question, Carlo Blasis, was neither an opera singer, a composer, nor a conductor. Instead, his correct designation would be option (c) ballet teacher and theorist.
Carlo Blasis was a pivotal figure in the world of ballet, greatly contributing to the art form by penning theoretical works and educating students in ballet technique. His influence extended beyond Italy as he spread his teaching philosophy and methods, which are recognized and utilized even in contemporary ballet education.