Final answer:
An EJB component is packaged in a .JAR file, which is used to aggregate multiple files for Java applications and libraries into a single archive.
Step-by-step explanation:
An EJB (Enterprise JavaBean) component is packaged in a .JAR (Java ARchive) file. This type of archive file is specifically used in Java to bundle multiple files into a single archive file that is platform-independent. The .JAR file format is used for aggregating many files into one, and it is essential for packing Java classes and associated metadata and resources (text, images, etc.) into one file for distribution. This is commonly used for distributing Java applications and libraries. In contrast, a WAR (Web ARchive) file is used for web applications, a RAR (Resource Adapter ARchive) file is used in Java EE for packaging resource adapters, and a DLL (Dynamic Link Library) is a file format used in Microsoft Windows for containing executable code or resources.