Final answer:
Nelson Mandela believed violence in social justice reform should be a last resort when peaceful methods fail, aligning with option D.
Step-by-step explanation:
Based on the understanding of the text, Nelson Mandela's belief about the use of violence to promote social justice reform is that it should only be considered when no other methods appear effective in achieving the desired results. Mandela's strategy largely focused on peaceful protest and attempting to show the white political and business leaders that getting rid of apartheid would make South Africa more prosperous. Nevertheless, after the Sharpeville massacre and the banning of ANC and PAC, Mandela and other activists felt compelled to consider sabotage and other forms of violence as tools for resistance amidst oppressive conditions. Therefore, the correct answer to the student's question is D) It is only to be considered when no other methods seem to get the desired results.