Final answer:
In Ravel's Bolero, the most emphasized musical feature is tone color, characterized by the repetition of a single theme that is passed among various instruments, each adding their own unique timbre to the piece. option a is correct.
Step-by-step explanation:
The musical feature most emphasized in Ravel's Bolero is tone color. Maurice Ravel's Bolero is renowned for its distinctive and repetitive melodic rhythm which is played by different instruments throughout the composition. This lends a unique timbre or tone color to the melody as it is passed around the orchestra.
Unlike thematic development, where a theme is evolved and transformed over the course of a work, Bolero maintains essentially the same theme that undergoes minimal developmental change. Instead, Ravel's focus on tone color is evident as each instrument brings its own color and character to the melody, creating a rich tapestry of sound without employing a wide variety of themes or polyrhythms.
It's important to note that Bolero does not prominently feature polyrhythms, as seen in traditional African music or complex thematic development common in other classical music compositions. The piece is also not characterized by a high degree of variety; instead, it is the repetition of the same theme with different instrumental timbres that defines the work. Ravel's intent was to experiment with orchestration and the differing sound qualities of orchestral instruments, which made tone color the essence of this piece.