This picture shows state troopers attacking civil rights demonstrators on March 7, 1965, which came to be known as "Bloody Sunday." As part of this movement, African Americans who wanted to vote participated in a series of marches called the Great Marches.

B) Children's Marches.
Eliminate

C) March on Washington, D.C.

D) Selma-to-Montgomery Marches

The Great Marches were a three protest carried out by African American citizens who wanted to show their desire to exercise their constitutional right to vote.

The marches began on Selma, Alabama with the objective of arrival to Montgomery, the State´s capital. During two of these marches, the protesters were attacked by the state troops. The first of the marches was then known as the "Bloody Sunday".

The attacks and the death of an African American civilian during the two marches created a social upheaviour throughout the nation that made that President Lyndon Johnson sent security for the marchers during the third and final march.

By highlighting racial injustice, these marches helped to the passing of the Voting Rights Act on that same year.

I hope this answer helps you.