The correct answer is A. WSDL.
WSDL stands for Web Services Description Language. It is an XML-based language that describes a web service. A web service is a self-contained, modular application that can be accessed over a network. WSDL defines the interface of a web service, including the operations that it supports and the data that it accepts and returns.
B. SCD stands for Service Component Definition Language. It is an XML-based language that describes the components of a service-oriented architecture (SOA). An SOA is a way of designing and building software applications that are loosely coupled and can be easily reused. SCD defines the components of an SOA, including the services that they provide and the data that they exchange.
C. XML is a markup language that is used to create documents that can be shared and processed by computers. XML is not specifically used to define the service component that performs the service.
D. None of the mentioned is not the correct answer.