किस भारतीय स्वतंत्रता सेनानी को लोकप्रिय रूप से 'भारत का लौह पुरुष' कहा जाता था?

Which of the following factors contributed to the growth of militant nationalism (extremism) in India in the early 20th century?

On which date in 1920 did the Khilafat Committee officially launch its Non-Cooperation Movement in All-India Hartal?