At what point in the ES installation process should Splunk_TA_ForIndexes.spl be deployed to the indexers?

At what point in the ES installation process should Splunk_TA_ForIndexes.spl be deployed to the indexers?
A . When adding apps to the deployment server.
B . Splunk_TA_ForIndexers.spl is installed first.
C . After installing ES on the search head(s) and running the distributed configuration management tool.
D . Splunk_TA_ForIndexers.spl is only installed on indexer cluster sites using the cluster master and the splunk apply cluster-bundle command.

Answer: C

Explanation:

Reference: https://docs.splunk.com/Documentation/ES/6.1.0/Install/InstallTechnologyAdd-ons