Assuming there are no custom properties defined in current plugin-cfg.xml file, what should be done before running the GenPluginCfg command?

Correct Answer: B 🗳️
Delete the plugin-cfg.xml file in the profile_root/config/cells directory before you use the GenPluginCfg command. Otherwise, configuration changes do not persist to the plugin-cfg.xml file. However, do not delete the plugin-cfg.xml file if you have custom properties that you previously set in it that you need to persist.
Note: You can update the global plugin-cfg.xml file using the administrative console or running the GenPluginCfg command for all of the clusters in a cell.
However, you must delete the config/cells/plugin-cfg.xml file before you update the global plugin-cfg.xml file. If you do not delete the config/cells/plugin-cfg.xml file, only the new properties and their values are added to the global plugin-cfg.xml file. Any updates to existing plug-in property values are not added to the global plugin-cfg.xml file.
Reference:
https://www.ibm.com/support/knowledgecenter/en/SSAW57_8.5.5/com.ibm.websphere.nd.doc/ae/rxml_genplugincfg1.html

An administrator installs IBM WebSphere Application Server and an HTTP server, but when configuring the environment, the administrator finds that the
WebSphere Plug-in is missing.
Which tool can be used to fix this issue?

Correct Answer: D 🗳️
In the WebSphere Integrated Solutions Console, the web server is represented as a specific server type, and you can view or modify all of the configuration properties used in the plugin-cfg.xml file for the web server plug-in from the WebSphere Integrated Solutions Console.
Reference:
https://www.ibm.com/support/knowledgecenter/en/SSHRKX_8.0.0/plan/plan_ihs.html

How can an administrator deploy or update an EAR, JAR, WAR, or SAR file to an application server or cluster in a development environment?

Correct Answer: A 🗳️
You can install an enterprise application file on an application server or cluster by dragging or copying an enterprise archive (EAR), web application archive
(WAR), Java archive (JAR), or Session Initiation Protocol (SIP) archive (SAR) to a monitored directory.
Reference:
https://www.ibm.com/support/knowledgecenter/en/SSAW57_8.5.5/com.ibm.websphere.nd.doc/ae/trun_app_install_dragdrop.html

An administrator notices that the Message Driven Beans (MDBs) are slow to complete, and decides to increase the "˜Maximum concurrent MDB invocations per endpoint'.
Which thread pool should be tuned to ensure it can run the maximum number of MDBs without waiting?

Correct Answer: D 🗳️
The thread pool WMQJCAResourceAdapter is referenced by the WebSphere MQ (WMQ) resource adapter inbound delivery to MDB's. When WebSphere MQ resource adapter is used in conjunction with the activation specs, the resource adapter's Work Manager uses the values defined for the
WMQJCAResourceAdapter for utilizing the total number of threads defined.
Ideally the default values provides for the WMQJCAResourceAdapter will be sufficient for the resource adapter. But in case there is an heavy load on the system processing huge number of messages, you can increase the maximum number of threads the thread pool can hold.
Reference:
http://www-01.ibm.com/support/docview.wss?uid=swg21383363