Which of the following was discontinued in April 1994?

The choice that was discontinued in April 1994 is the Combined Warning Bulletin. This bulletin was used within the payment processing industry to inform stakeholders about merchants that had previously exhibited potentially fraudulent behavior or other reasons that warranted caution. The discontinuation of this bulletin reflects changes in industry practices and the evolution of how merchants are monitored and reported on, which increasingly relied on more centralized data and technology solutions to manage risk and enhance security in transaction processing.

The other options are related to different aspects of payment processing and data handling but were not specifically discontinued in April 1994. Understanding this context highlights the importance of monitoring and maintaining current systems for credit risk and fraud detection in the evolving landscape of electronic transactions.