What Is One Obligation That the General Data Protection Regulation

What is one obligation that the General Data Protection Regulation (GDPR) imposes on data processors?

A) To honor all data access requests from data subjects.
B) To inform data subjects about the identity and contact details of the controller.
C) To implement appropriate technical and organizational measures that ensure an appropriate level of security.
D) To carry out data protection impact assessments in cases where processing is likely to result in high risk to the rights and freedoms of individuals.