Which cytoplasm in rice is most widely used as source of male sterility?

Correct option is C

Hybrid rice production uses cytoplasmic male sterility systems.
Wild abortive (WA) cytoplasm is most widely used. It provides stable male sterility expression.
Many commercial rice hybrids are based on WA-CMS. Other CMS sources are less commonly utilized. Thus CMS-Wild abortive is correct.