Which of the following statements are correct?
I. In 1895, Mahatma Gandhi established the Natal Congress to fight against racial discrimination in South Africa.
II. In Ahmedabad, Mahatma Gandhi led a successful millworkers’ strike in 1919.
III. In 1919, Gandhiji gave a call for a satyagraha against the Rowlatt Act.
IV. On learning about the Jallianwala Bagh massacre, Mahatma Gandhi renounced his knighthood.