निम्नलिखित में से कौन सा भारी उपधातु/तत्व भूजल में अत्यधिक विषैले प्रदूषक के रूप में व्यापक रूप से जाना जाता है, जिससे गंगा के डेल्टा जैसे क्षेत्रों में बड़े पैमाने पर विषाक्तता होती है?

Which Indian independence movement leader was primarily known for his philosophy and practice of non-violent civil disobedience?

Who gave the call for 'Do or Die' during the Quit India Movement in 1942?

Which of the following revolutionary pairs were imprisoned together in Cellular Jail and faced harsh conditions, contributing significantly to the Indian independence movement?