Choose the correct adverb to fill in the blank:

The musician played the guitar __________.

well

The correct answer is option (2) well.

An adverb is needed to describe how the musician played the guitar. "Well" is the appropriate adverb here as it describes the manner in which he played, indicating that he played with skill or proficiency. Options (1), (3), and (4) are not adverbs and do not appropriately describe the manner of playing.