Option 1: Sardar Patel and Jawahar-lal Nehru were both important figures in the Indian independence movement, but they did not work together specifically to integrate the princely states into the Indian Union. Nehru focused more on foreign diplomacy and international relations.

Option 3: Sardar Patel and Mahatma Gandhi both played crucial roles in the Indian independence movement, but Gandhiji primarily focused on nonviolent civil disobedience and political resistance. He did not directly contribute to the integration of princely states.

Option 4: Sardar Patel and K M Munshi were both prominent leaders in the Indian independence struggle, but Munshi primarily focused on literature and education. He did not have a significant role in the integration of princely states.

Option 2: Sardar Patel and V.P. Menon were the key figures who worked together to merge the princely states into the Indian Union. Sardar Patel was responsible for negotiating with the rulers of the princely states, while V.P. Menon played a crucial role in implementing these agreements and ensuring the smooth integration of these states. This option accurately identifies the pair that contributed significantly to integrating the princely states into the Indian Union.