Answer:
B: the repetition of the line "Let my people go"
Step-by-step explanation:
The part of the song "Go Down, Moses" that most emphasizes its singers' demand for freedom is the repetition of the line "Let my people go" because this was the purpose for Moses having to go down to Egypt: to free God's people from the oppression under pharaoh. Also the instruction words to be said to the ruler, and to bring freedom to the Israelites.