How was the civil rights movement both violent and nonviolent? which was more effective?

The Civil Rights movement was non-violent in that those taking a stand would participate in boycotts (bus boycotts), sit-ins and marches or protests. There were also times when there were riots. I feel that both ended up being effective but that the non-violent forms of resistance were most effective. 

The answer b is correct this all occurred during the red scare