https://docs.splunk.com/Documentation/Splunk/8.2.2/Updating/Aboutdeploymentserver
"The deployment server is the tool for distributing configurations, apps, and content updates to groups of Splunk Enterprise instances."

Reference:https://docs.splunk.com/Documentation/Splunk/8.2.3/Admin/Groups,stacks,pools, andotherterminology When using license pools, volume allocations apply to indexers. A license pool is a group of indexers that share a certain amount of daily indexing volume. The license pool specifies how much data each indexer can index per day, as well as which indexes are available for each indexer. Therefore, option A is the correct answer. References: Splunk Enterprise Certified Admin | Splunk, [Set up and manage license pools - Splunk Documentation]

Reference:https://docs.splunk.com/Documentation/Splunk/8.2.3/Admin/Aboutusersandroles The power role is a default Splunk role that grants users the ability to create saved searches, edit shared objects and alerts, and access advanced search commands. However, the power role does not allow users to create custom roles, which is a privilege reserved for the admin role. Therefore, option B is the correct answer. References: Splunk Enterprise Certified Admin | Splunk, [About configuring role-based user access - Splunk Documentation]

A Splunk deployment server is a system that distributes apps, configurations, and other assets to groups of Splunk Enterprise instances. You can use it to distribute updates to most types of Splunk Enterprise components: forwarders, non-clustered indexers, and search heads2.
A Splunk deployment server is available on every full Splunk Enterprise instance. To use it, you must activate it by placing at least one app into %SPLUNK_HOME%\etc\deployment-apps on the host you want to act as deployment server3.
A Splunk deployment server maintains the list of server classes and uses those server classes to determine what content to distribute to each client. A server class is a group of deployment clients that share one or more defined characteristics1.
A Splunk deployment client is a Splunk instance remotely configured by a deployment server. Deployment clients can be universal forwarders, heavy forwarders, indexers, or search heads. Each deployment client belongs to one or more server classes1.
A Splunk deployment app is a set of content (including configuration files) maintained on the deployment server and deployed as a unit to clients of a server class. A deployment app can be an existing Splunk Enterprise app or one developed solely to group some content for deployment purposes1.
Therefore, option C is correct, and the other options are incorrect.