The correct answer is B "Public concert in the square Saturday night: All sections open to the public."
This is the correct answer because the Civil Rights Act of 1964 made it illegal for discrimination based on race to take place in public places such as movie theaters, concert venues, restaurants, hotels, etc. The statement in the question would break this law, as it enforces segregation. So changing it to letter B would make it so that all people have an equal opportunity to see the concert.