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.

http://www.splunk.com/view/SP-CAAAGPR

https://docs.splunk.com/Documentation/Splunk/7.0.3/Forwarding
/Routeandfilterdatad#Perform_selective_indexing_and_forwarding
Specifies a comma-separated list of tcpout group names. Use this setting to selectively forward your data to specific indexers by specifying the tcpout groups that the forwarder should use when forwarding the data.
Define the tcpout group names in the outputs.conf file in [tcpout:<tcpout_group_name>] stanzas. The groups present in defaultGroup in [tcpout] stanza in the outputs.conf file.

In Splunk Enterprise, when knowledge bundles (which include lookup files, configurations, and other knowledge objects) are replicated between search heads and indexers, administrators can control the maximum size of lookup files that are eligible for replication.
The correct parameter to use is excludeReplicatedLookupSize, defined in distsearch.conf. This parameter specifies a maximum file size (in megabytes) beyond which lookup files are excluded from bundle replication. By setting this to 500, any lookup file larger than 500 MB will not be replicated to search peers.
This is especially important for performance optimization and preventing unnecessary network load during search head to indexer communication.
Example configuration (distsearch.conf):
[replicationSettings]
excludeReplicatedLookupSize = 500
Reference (Splunk Documentation):
* distsearch.conf.spec and example # excludeReplicatedLookupSize
* Splunk Enterprise Distributed Search Manual # "Control knowledge bundle replication between search heads and indexers"
* Splunk Admin Manual # "Prevent large lookup files from being replicated"

https://docs.splunk.com/Documentation/Splunk/8.2.2/Data/UsetheHTTPEventCollector
"The HTTP Event Collector (HEC) lets you send data and application events to a Splunk deployment over the HTTP and Secure HTTP (HTTPS) protocols. HEC uses a token-based authentication model. You can generate a token and then configure a logging library or HTTP client with the token to send data to HEC in a specific format. This process eliminates the need for a Splunk forwarder when you send application events."