The statement that best explains the reason Congress passed the Fifteenth Amendment is:
• to protect the ability of Freedmen to participate in choosing a government through voting.
The Fifteenth Amendment, ratified in 1870, prohibits the federal and state governments from denying a citizen the right to vote based on "race, color, or previous condition of servitude," thereby aimed at ensuring that Freedmen (formerly enslaved individuals) could participate in the electoral process.