African rock art gives evidence that a giant lake existed in the sahara desert during the last ice age in present-day sudan.

What role do background vocalists play? a. they provide additional support to the main vocalist and other members of a music group during recording sessions and live events. b. they perform as part of orchestras working for music theaters. c. they mix different songs or music scores and present a unique blend of music to an audience. d. they assemble and organize musical compositions according to their clients’ requirements.