Finish this statement correctly.
"the key traits of early rock and roll were the driving backbeat, electric guitar, and loud, amplified volume."

simple harmonies

difficult melody

vocal line

microphones

Vocal line

Explanation:

Rock and roll originated in the United States in the late 1940s and early 1950s. It was heavily influenced by jazz, blues, and country music, taking several elements from these genres to become a completely revolutionary style. One of the most important changes brought on by rock and roll was the idea of replacing the traditional big jazz band by a small group of performers, however different from the traditional solo artists playing blues, with a vocalist carrying a simple and catchy melody, with the intent of making the audience dance. Also, pianos were commonly used in jazz but impractical to use outside of ballrooms and thus were replaced by the new electric guitars, that had the volume to perform in front of big crowds and yet were easily transported and handled on stage.

they are often in theme and variations