C - Beautiful antique instruments renames guitars
Appositives are nouns or noun phrases that renames another noun beside it. The phrase 'beautiful antique instruments' renames and is right beside 'guitars' as it is describing them.
This passage does have the claim about the movie's quality. The soundness of the reasoning is relative to the evaluators ideals. Sound reasoning means simply that it is reasoning which makes sense, or is logical. The writer states their discontent for the movie, but lacks reasoning for the over length, poor acting, and boring music. To the individual evaluating, is was distasteful. I would probably say option A.
A. Suddenly B. Very C. Softly
Hopefully this helps ; tells you the answer !