Final answer:
The distinctive progressive rock sound emerged from a combination of rock with jazz and classical music, which gave rise to its elaborate and sophisticated style.
Step-by-step explanation:
The distinctive sound of progressive rock, also known as prog rock, emerged in the late 1960s and early 1970s as a fusion of rock with other musical genres. Specifically, the question asks which genres were combined with rock to create progressive rock.
The correct answer is A) Jazz and Classical. Progressive rock bands often incorporated elements such as extended compositions, complex rhythms, and the use of symphonic orchestration, drawing heavily from the sophistication of jazz and the grandeur of classical music.
This combination led to progressive rock's unique and elaborate sound, characterized by its ambitious scope and musical virtuosity.