Question 19.

Option A and option D both signifies the inspiration of folk music from two different times. Folk is not limited to immediate past or to any specific time-line. This contributes to the plurality of folk music.

Option C talks about "fluidity". Fluidity indicates flexibility or different modes of oral rendition. For example different vocal styles can be generated by pitch, rhythm, style of rendition. Hence, the variance in oral transmission of music can lead to various iterations of one original form. Hence, this again contributes to the diversity and plurality of folk music.

Option B: Popularity or unpopularity is an opinion. An opinion in no way contributes to the diversity of a folk form. It might be regarded as diverse opinions but does not inherently contribute to the diversity of folk itself. Hence, option B does not contribute to folk's plurality.