Answer:
many activists in the 1960s felt that other ways of influencing policy were not effective enough.
The option that best completes the diagram is "many activists in the 1960s felt that other ways of influencing policy were not effective enough."
The 1960s were difficult years in the United States. Many changes started to happen and some civil rights movements organized by young people expressed its opposition to political decisions such as the participation of the US in the War of Vietnam. Some of these organizations grew and became more formal and realized that the most effective way to exert pressure was by lobbying with legislators. From that time on, interest groups hire lobbyists and lobbying firms to negotiate with congressmen.
btw* this is not by me, this is something I searched up and someone else answered this which was scouteo
btw= by the way