What are the obligations of a processor that engages a sub-processor?

What are the obligations of a processor that engages a sub-processor?
A . The processor must give the controller prior written notice and perform a preliminary audit of the sub- processor.
B . The processor must obtain the controller’s specific written authorization and provide annual reports on the sub-processor’s performance.
C . The processor must receive a written agreement that the sub-processor will be fully liable to the controller for the performance of its obligations in relation to the personal data concerned.
D . The processor must obtain the consent of the controller and ensure the sub-processor complies with data processing obligations that are equivalent to those that apply to the processor.

Answer: C

Explanation:

Reference: https://inplp.com/latest-news/article/gdpr-rights-and-obligations-of-sub-processors/