Pablo Casals was a famous Spanish cellist who is widely considered as a prodigy or one the best cellist. After Franco became a dictator in Spain, he left the country and went to the United States. There, he composed and played on many occasions. One time he played for the President John F. Kennedy and he awarded Casals with the Presidential Medal of Freedom because of his contributions to music and culture.
In "Young Pablo Casals" the conductor throws his arms around Pablo because the conductor was overwhelmed by Pablo's Playing, option D. This can be explained because Pablo was an eminent prodigy and could play beautiful music.