Explanation:

Nathpanthis, Siddhacharas and Yogis:
They advocated renunciation of the world. Hence, option (a) is correct.
To them the path to salvation lay in meditation on the formless Ultimate Reality and the realisation of oneness with it.
To achieve this they advocated intense training of the mind and body through practices like yogasanas, breathing exercises and meditation.
These groups became particularly popular among “low” castes.
Their criticism of conventional religion created the ground for devotional religion to become a popular force in northern India.