Final answer:
A Natural Sign in music tells a musician to play the note as its natural pitch, cancelling any previous sharps or flats. It ensures the note is played without alteration.
Step-by-step explanation:
A Natural Sign in music notation is an important symbol that tells a musician to play the note without any alteration, effectively cancelling any previous sharps or flats that may have affected the note in the score. The correct answer is 4) To cancel the previous accidental marking.
Notes like A-sharp, C, or E-flat are altered by accidentals, and a natural sign directly before a note indicates that the note should be played as its natural or unaltered pitch, regardless of any sharps or flats that may appear in the key signature or as accidentals earlier in the measure. This is crucial for maintaining the intended harmony and melody within a piece of music.