Your company has acquired ABC Company and will be building infrastructure for the merged entity. Now, You have a variety of mainframe applications, client server applications, and standalone programs that need to be integrated. Which of the following will provide a unified platform for scalable, secure SOA development? Choose one answer.

An Enterprise Service Bus (ESB) provides the fundamental infrastructure to integrate diverse systems (mainframe, client-server, standalone) under a unified, scalable, and secure Service-Oriented Architecture (SOA). JAXB and JAXR are Java-specific APIs for XML binding and registries, while SOAP and REST are communication protocols rather than integration platforms.