निम्नलिखित पारिस्थितिकीविदों में से किसने सबसे पहले पारिस्थितिक पिरामिड की अवधारणा प्रस्तुत की थी?

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?