The correct answer is Chaitanya .

The Nirguna School of Bhakti is a school of Hindu philosophy that believes in the formless aspect of God. It emphasizes that God is beyond attributes and cannot be described by any qualities or characteristics. The followers of this school of thought believe that the ultimate goal of human life is to attain union with God.

Bhakti saints were the proponents of this school of thought, and they played a significant role in spreading the teachings of the Nirguna School of Bhakti. Kabir, Nanak, and Dadu were all Bhakti saints who belonged to the Nirguna School of Bhakti.

Kabir was a 15th-century Indian mystic poet who belonged to the Nirguna School of Bhakti. His poetry emphasized the importance of devotion to God and the need to transcend the limitations of the material world.

Nanak was the founder of Sikhism and a prominent Bhakti saint who belonged to the Nirguna School of Bhakti. He emphasized the importance of devotion to God and the need to live a righteous life.

Dadu was a 16th-century Indian saint who also belonged to the Nirguna School of Bhakti. He emphasized the importance of devotion to God and the need to attain union with the divine.

Chaitanya, on the other hand, was a 16th-century Indian saint who belonged to the Saguna School of Bhakti. The Saguna School of Bhakti emphasizes the worship of a personal God with attributes and qualities. Chaitanya propagated the worship of Lord Krishna as the supreme God and emphasized the importance of devotion to Krishna.

In conclusion, while Kabir, Nanak, and Dadu belonged to the Nirguna School of Bhakti, Chaitanya belonged to the Saguna School of Bhakti.