निम्नलिखित में से किस नदी को भारत में, विशेष रूप से इसके शहरी क्षेत्रों में, सबसे अधिक प्रदूषित माना 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?