In the first years of the twentieth century, was perceived as a threat to the "moral, spiritual, mental, and even physical well-being" of the nation.
a. ragtime
b. bebop
c. big band jazz
d. downhome blues

The correct answer to your question is A - ragtime. 

Ragtime was a musical style heavily relied on rhythmic syncopation but at the same time still having different characteristics that one can find in popular songs, catwalks, or even marches(!) from the end of the 19th century. It first appeared in Chicago.