Reference:https://community.splunk.com/t5/Getting-Data-In/Splunk-forwarder/m-p/18009 The forwarder that is recommended by Splunk to use in a production environment is the universal forwarder.
The universal forwarder is a lightweight Splunk agent that forwards data to indexers or other forwarders. The universal forwarder has a small footprint and consumes minimal system resources. It also supports secure and reliable data forwarding with encryption and acknowledgement features. Therefore, option D is the correct answer. References: Splunk Enterprise Certified Admin | Splunk, [About forwarding and receiving data - Splunk Documentation]