Correct Answer: C
A lead supervisory authority (LSA) is the main point of contact for organisations that process personal data across multiple EU member states. The LSA is responsible for coordinating cross-border investigations, issuing binding decisions, and enforcing GDPR compliance1. Cross-border processing is the main concern of the LSA, as it involves data processing activities that affect data subjects in more than one member state, or that take place in more than one member state2. The other options are not the main concern of the LSA, as they are either covered by the national supervisory authorities of each member state, or are not specific to cross-border processing. Reference: Is it possible to choose your lead supervisory authority under the GDPR?, Art. 56 GDPR - Competence of the lead supervisory authority, Navigating GDPR Compliance with a Lead Supervisory Authority, Guidelines 8/2022 on identifying a controller or processor's lead supervisory authority