शिक्षा से संबंधित 6वें मूलभूत कर्तव्य को किस संवैधानिक संशोधन द्वारा जोड़ा गया?

The 'Drain of Wealth' theory was propounded by which Indian nationalist leader?

Which event is considered the turning point in Mahatma Gandhi's leadership in the Indian independence movement?

Which African leader is known for his non-violent opposition to colonial rule?