Step 1: Understanding Gandhian philosophy.
Gandhian philosophy emphasizes non-violence, truth, and the promotion of social and political freedom. Some of the core principles are:
- Non-violence and Satyagraha are central to his philosophy, advocating for peaceful resistance.
- Swaraj is the concept of self-rule, which was the foundation of India's freedom struggle.
- Annihilation of Caste, though an important issue in Indian society, was primarily addressed by Dr. B.R. Ambedkar, not Gandhi.
Step 2: Conclusion.
The correct answer is 3. Annihilation of Caste.
Final Answer:
\[
\boxed{\text{The correct answer is 3. Annihilation of Caste.}}
\]