39.
Your Answer is
Correct Answer is A
Explanation
all the while always, always, conforms to the semantics here.
Item B: "During the interval", according to the context, the music is always playing, not the interval.
Item C: "Therefore", there is no causal relationship before and after.
Item D: The pronoun our is inconsistent with the pronoun in this paragraph. This paragraph uses the third person pronoun they as the referent.