In a spiritual, the part sung by the chorus seldom changed because the chorus
a.
was an african tradition.
c.
played the role of the lord.
b.
sang the refrain.
d.
let everyone take part.

The chorus sang the refrain. In most songs, the "chorus" refers to the part that is repeated. It does not necessarily mean that everyone took part, so you can go ahead and rule out option D. There is also no indication that the chorus took the part of the Lord, so you can also eliminate that option. Option A is too broad, so that can also be eliminated, leaving you only one answer. Hope this helps.

This is “sad”hope this !