दी गई श्रृंखला को तर्कसंगत रूप से पूरा करने के लिए निम्नलिखित में से कौन-सा अक्षर-संख्या समूह प्रश्न चिह्न (?) का स्थान लेगा? ZLG20, GSN30, NZU40, UGB50, ?

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?