Who among the following was known as a Nirguna saint and reformer?

Sant Kabir
Surdas
Chaitanya Mahaprabhu
Tulsidas

The correct answer is A. Sant Kabir.

Sant Kabir was a 15th-century Indian mystic poet and saint who is considered one of the most important figures in the Bhakti movement. He was born into a Muslim family in Varanasi, but he rejected the religious and social conventions of his time. He is known for his teachings on the unity of God and the equality of all people. He is also known for his use of simple language and his ability to reach out to people from all walks of life.

Surdas was a 16th-century Indian poet and saint who is considered one of the greatest composers of devotional songs in the Braj language. He was born blind, but he is said to have had a vision of Krishna when he was just a child. He is known for his love of Krishna and his devotion to him. He is also known for his beautiful songs, which are still sung today by Hindus all over the world.

Chaitanya Mahaprabhu was a 16th-century Indian saint and reformer who is considered one of the most important figures in the Vaishnava movement. He was born in Bengal and is said to have been a reincarnation of Krishna. He is known for his teachings on the love of God and his emphasis on devotion and service to God. He is also known for his ecstatic dancing and singing, which attracted many followers.

Tulsidas was a 16th-century Indian poet and saint who is considered one of the greatest writers in the Hindi language. He is best known for his epic poem Ramacharitamanasa, which tells the story of Rama, one of the most important figures in Hinduism. He is also known for his devotional songs and his teachings on the importance of devotion to God.

In conclusion, the correct answer is A. Sant Kabir.