वह लुप्त संख्या ज्ञात कीजिए जो तार्किक रूप से श्रृंखला में फिट बैठती है: 6, 12, 20, 30, ?

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?