The standard for validating off-the-shelf payment applications used in authorization and settlement is:

The correct choice is PA-DSS because it stands for Payment Application Data Security Standard. This standard specifically addresses security requirements for third-party payment applications that are used in conjunction with payment card transactions. It outlines the necessary measures that developers must implement to ensure that their applications do not store sensitive cardholder data, such as full magnetic stripe data, CVV, or PINs, and that they support compliance with PCI DSS when integrated into payment processing.

The focus of PA-DSS is on ensuring that payment applications are built with security in mind to protect cardholder data during the authorization and settlement processes. By validating off-the-shelf payment applications according to PA-DSS, organizations can significantly reduce the risk of security vulnerabilities, thereby helping to protect the integrity of payment card transactions.

The other standards mentioned serve different purposes: ASV (Approved Scanning Vendor) pertains to scanning and vulnerability management, SAQ (Self-Assessment Questionnaire) is for merchants who handle card data in lower risk environments, and ROC (Report on Compliance) involves a formal assessment process for organizations that must demonstrate PCI DSS compliance at a higher level. Each of these has its distinct role in the realm of PCI compliance but is not specifically aimed at validating payment applications like PA-DSS is.