Explanation:

Let’s look at the options:

- Option 1: Ishwarchandra Vidyasagar

- He was a great social reformer and educator in Bengal.

- He promoted widow remarriage and education for women.

- He did not found the Brahmo Samaj.

- Option 2: Aurbindo

- Likely refers to Sri Aurobindo, a noted philosopher and nationalist leader.

- Known for his spiritual and philosophical work but not for founding Brahmo Samaj.

- Not the founder.

- Option 3: Keshava Chandra Sen

- He was a prominent Brahmo Samaj leader and reformer.

- He played a major role in popularizing the movement, but did not found it.

- Not the founder.

- Option 4: Chaitanya

- Refers to Chaitanya Mahaprabhu, a revered saint associated with Bhakti movement in Bengal.

- He lived much before the Brahmo Samaj era and was not involved.

- Not the founder.

- Correct Answer: The Brahmo Samaj was actually founded by Raja Ram Mohan Roy in 1828, not by any of the options provided.