लवणीय जल को मीठे पानी में बदलने (विवणीकरण) के लिए मुख्य रूप से और व्यापक रूप से निम्नलिखित में से किस प्रक्रिया का उपयोग किया 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?