The correct answer to this open question is the following.
Although no text is provided, we can say that Edwina and Marshall Johnson had trouble with the Montgomery bus laws because they came from New Jersey, a state that had no racial problems as happened in Alabama. So these two brothers were unaware of the segregation regulations in Montgomery Alabama and that is why they did not pay attention to the signs that stated that those seats in the bus were reserved to white people.
These two young siblings were visiting some relatives in 1949. So when the bus driver called the police, they were sent to jail for violating the segregation laws. Judge Wiley C. Hill threatened to send them to reform school u of the city of Montgomery, Alabama.
