Final answer:
The object used to group similar types of events is 'Event tags'. These are used in systems like the CXone Expert framework to link related content for organizational efficiency.
Step-by-step explanation:
The knowledge object that can be used to group similar types of events is d) Event tags. In the context of the CXone Expert framework, tags are instrumental in dynamically organizing content. They function by linking pages or events along common themes, thereby grouping related events for better classification and retrieval. Utilizing tags effectively can vastly improve the structure and efficiency of content management.