The correct answer is D) they expressed the soldiers' feelings as they marched into battle.
Songs like the "War Song. 1776" were important to American Revolutionary soldiers because they expressed the soldiers' feelings as they marched into battle.
These kind of songs were important during the bloody fights in the American Revolution in that were sung by the soldiers while marching to the battlefield or were at camp. The songs served to express the moments the soldiers were living in battle and also motivated them to keep fighting hard.