Grandmaster Flash Is Credited with Creating What Techniques in Rap

Grandmaster Flash is credited with creating what techniques in rap music?

A) Flash was notorious for simply copying other rappers' styles.
B) Flash began the rap music tradition of using female backup singers.
C) Flash began the use of "scratching" and manipulating turntable speeds.
D) He is generally credited with beginning the inner city style known as "gangsta rap."