पृथ्वी और बहुत पुरानी भूवैज्ञानिक संरचनाओं की आयु का अनुमान मुख्य रूप से किस विधि का उपयोग करके लगाया 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?