Final answer:
The technology that could be used to verify that the report was indeed sent by the branch manager is a digital signature. Therefore, the correct option is 'c. Digital signature'.
Step-by-step explanation:
A regional manager can use a digital signature to verify the authenticity of a financial document sent by a branch manager, as it ensures both the identity of the sender and the document's integrity. The technology that could be used to verify that the report was indeed sent by the branch manager is a digital signature.
A digital signature is a cryptographic technique that verifies the authenticity and integrity of digital documents. It uses a unique key generated by the sender to create a digital signature, which is then attached to the document. This signature can be verified by the recipient using the sender's public key, ensuring that the document was not tampered with and was indeed sent by the branch manager. Unlike other options mentioned (anti-hack, virtual private network, firewall), a digital signature specifically addresses the concern of verifying the authenticity of a document sent by a specific individual or entity.