Option a is the correct answer. Sant Bhasha refers to the language used by the Nirguna mystics in their spiritual and devotional compositions. The term "Sant Bhasha" translates to "language of the saints" and is associated with the devotional poetry and teachings of the Bhakti movement in medieval India. The Nirguna mystics, such as Kabir, Namdev, and Guru Nanak, emphasized the formless and attributeless nature of the divine, focusing on the spiritual realization of a higher truth beyond the confines of religious rituals and societal divisions. Their compositions in Sant Bhasha often expressed their devotion, philosophical insights, and social criticism.