What is SQL injection and why is it relevant to PCI DSS?

• A.An attack where malicious SQL code is inserted into application queries, potentially allowing unauthorized access to cardholder data in databases
• B.A data backup method, because scan frequency may be reduced to annual where no vulnerabilities were found previously for outsourced payment pages
• C.A database optimization technique, which Requirement 3.2.1 subjects to documented retention limits and a process at least every three months to find and securely delete anything exceeding them
• D.A network scanning technique, on the basis that secure coding training for developers is required once at induction only for e-commerce merchants