प्रतिवर्ष 'विश्व पृथ्वी दिवस' किस दिन मनाया जाता है?

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?