Final answer:
Sebastian's reaction to the concert was one of deep disappointment, expressing that the event was ruined. There is no information provided about the number of concerts he's performed or the number of musicians. The concert was anticipated to be the pinnacle of his career.
Step-by-step explanation:
Sebastian's reaction to the concert was one of despair and disappointment, as he expressed that the concert was ruined and completely destroyed. This indicates that the concert did not meet his expectations or standards, severely impacting his sentiment. A. Sebastian felt the concert was a disaster.
While the text implies that he considers the concert a significant event in his career, it does not provide specific information regarding B. the total number of concerts he has performed nor D. the number of musicians in his orchestra. C. Before the concert, it seems Sebastian viewed his career as distinguished, and the concert was meant to be a high point or pinnacle of his career.