Which statement describes a characteristic of plainchant music?
a. it was performed by troubadours
b. it was secular music
c. it was performed without instruments.
d. it was performed with multiple parts singing different harmonies

Even though is tru that the D. option is one of the characteristics of this type of music, The one that perfectly describes it is the C. option: It was performed with no instruments. This type of music is very similar to the gregorian musica and there is an absense of instruments.

Normally it is at the top left, above where the music starts.