A.I. Explanation:

Option 1: "To protest against the British government's policies."

Explanation: This option is incorrect because the text does not mention Gandhi fasting as a protest against British policies. Instead, it highlights his focus on unity between Hindus and Muslims during a time of conflict, which is not aligned with this option.

Option 2: "To demonstrate his support for nonviolent resistance."

Explanation: While Gandhi was known for his nonviolent resistance, the text specifically states that he was fasting and praying for unity between Hindus and Muslims, not merely to demonstrate support for nonviolence. Therefore, this option lacks the specific context provided in the text.

Option 3: "To pray for unity between Hindus and Muslims."

Explanation: This option is correct as the text explicitly states that Gandhi was in Calcutta fasting and praying for unity between Hindus and Muslims. This directly aligns with the main idea of his actions during that time, emphasizing his commitment to peace and unity.

Option 4: "To celebrate India's independence in solitude."

Explanation: This option is incorrect because the text indicates that Gandhi chose to fast and pray for unity rather than celebrating independence. His absence from the ceremony was not for celebration but for a solemn purpose, which contradicts the idea of celebrating in solitude.