A is correct. The default OC4J instance is named home. 
B, C, and D are wrong because there are no such default OC4J instances.

B and C are correct. B is correct because you must only specify the location attribute when looking up a non-emulated data source in the JNDI tree. C is correct because you must specify all three attributes for emulated data sources, although only the ejb-location attribute is used by the applications, servlets, JSPs, and EJBs. 
A is wrong because you must specify all three attributes for emulated data sources, and D is wrong because you must specify only the location attribute for a non-emulated data source.

C is correct. The opmnctl startproc process-type=OC4J command will start all OC4J instances in an OracleAS instance. 
A is wrong because the ias-component option starts only the specified OC4J instance, not all OC4J instances. B is wrong because the process-type option can’t be used to start a single instance of OC4J. C is wrong because the command is missing the process-type option.
 

A is correct. The server.xml file is the main OC4J configuration file. 
B is wrong because the web.xml file contains the Web configuration information. C is wrong because the oc4j_module is part of the Oracle HTTP Server configuration, not the OC4J configuration. D is wrong because the application.xml is the key configuration file for an application, not the OC4J instance. 

B is correct. You use EAR files to deploy J2EE applications. 
A is wrong because WAR files are used to deploy Web applications, not J2EE applications. C is wrong because JAR files are used to deploy client applications only. D is wrong because it refers to a nonexistent type of file. 

C is correct. The mod_oc4j module is part of the Oracle HTTP Server, and it is instrumental in facilitating communications between the Web server and the OC4J instance.
A and B are wrong because the oc4j_module isn’t a configuration file but an HTTP module. D is wrong because the oc4j_module has nothing to do with the OC4J configuration. 

A is correct. Data sources are published in the Java Naming and Directory Interface ( JNDI).
B, C, and D are the wrong locations for publishing the data sources. 

A is correct. The OC4J-specific global configuration file is named orion-application.xml (all OC4J-specific files have the orion prefix in the XML files).
B is wrong because the server.xml file is the main configuration file for the OC4J instance. C is wrong because the application.xml file is the main J2EE-specific application configuration file. D is wrong because it refers to a nonexistent configuration file.

D is correct. When you deploy a Web application for the first time, its WAR file is wrapped into an EAR file.
A, B, and C are wrong because they provide the wrong filenames.

B is correct. You must use a non-emulated data source to access multiple databases.
A is wrong because an emulated data source will let you connect only to a single database instance. C is wrong because the default data source (OracleDS) is an emulated data source that allows you to connect to just a single Oracle database. D is wrong because you must use a datasource file when you’re using data sources.