Final answer:
Scott Joplin popularized the genre of Ragtime music, notably through his composition 'Maple Leaf Rag', which was influential in American music and preceded the jazz era.
Step-by-step explanation:
The type of music that Scott Joplin popularized was c) Ragtime. Scott Joplin was an African American composer and a prominent figure in the creation and spread of ragtime music at the turn of the 20th century. Renowned for his hit composition, "Maple Leaf Rag," Joplin played a pivotal role in the establishment of ragtime as a significant and uniquely American musical genre. His music gained widespread popularity through the sale of sheet music, and he inspired various other musicians, contributing to the diverse soundscape of American music that later evolved into other styles such as jazz.