Which one of the following caste of termite is sterile?

Answer: Option C

Among the given options soldiers caste of termite is sterile.
Castes of termites are primarily divided into two types of individuals: fertile (reproductives) and sterile individuals (neuters).
The sterile castes include workers, presoldiers and soldiers, while the fertile ones are alates, primary reproductives and secondary reproductive.
Soldier termites have distinctively shaped heads and are typically bigger than workers. Their protruding mandibles help them protect their colonies. Soldiers have elongated bodies and are pale red, light brown, or white.