Final answer:
William's extreme attitude can be attributed to group polarization, which is the strengthening of the original group attitude after discussing views within the group.
Step-by-step explanation:
William's extreme attitude can be attributed to group polarization (b). Group polarization is the strengthening of the original group attitude after discussing views within the group. In this case, after attending the People's Temple worship service and being exposed to the group's beliefs and attitudes, William became more committed to serving the People's Temple and participating in anti-segregation protests.