Explanation:

- First Round Table Conference:

- Held from November 1930 to January 1931 in London.

- Aimed to discuss constitutional reforms in India.

- Mahatma Gandhi did not attend as he was not released from prison at the time.

- Second Round Table Conference:

- Took place from September to December 1931.

- Gandhiji participated as the sole representative of the Indian National Congress.

- The discussions were largely unsuccessful in meeting Indian demands.

- Third Round Table Conference:

- Conducted from November to December 1932.

- Neither the Indian National Congress nor Gandhi participated as they were boycotting it.

- Correct Answer: Option 2 - Second

- None:

- Incorrect as Gandhi did participate in the second conference.

Gandhiji's participation in the Second Round Table Conference was a significant political event, although it did not yield the desired results for Indian self-governance.