Read the sentence given below to find out whether there is any grammatical error in it. The error, if any, will be in one part of the sentence. The corresponding letter of that part is the answer. If the sentence is error-free then, choose “No error” as the answer. (Ignore the errors of punctuation, if any.)

The soothing melody (A)/ of the violin echoed through (B)/ the opulently concert hall, (C)/ captivating the audience. (D)

Correct option is C

The error in the sentence is in part (C). The adjective "opulently" is incorrectly used and should be the adjective "opulent." "Opulently" is an adverb and cannot modify the noun "concert hall." The correct form is "opulent," which is an adjective.
Corrected sentence: The soothing melody of the violin echoed through the opulent concert hall, captivating the audience.