Concept:Achal swar are fixed notes that never change from their pure (shuddh) form.
Explanation:There are seven swaras in the Indian scale: Sa, Re, Ga, Ma, Pa, Dha, Ni.
Among them, Shadja (Sa) and Pancham (Pa) are always pure and never become komal or tivra.
These two are called Achal, meaning immovable or constant.
The other five swaras (Re, Ga, Ma, Dha, Ni) can be altered and are called Vikrut or movable.
Answer:C. SA - PA