Answer:
B. assumed public office
Step-by-step explanation:
Within a week after the passage of the Voting Rights Act of 1965, African Americans in several cities "assumed public office."
To assume public office means taking up responsibility, which African Americans did immediately after the Voting Rights Act of 1965 is passed by the United States Congress.
Option A is not correct because African Americans did not riot.
Also, option C is not correct because President Johnson was reelected in 1964
Option D is also not correct because African Americans did not move to the suburbs.