Reference: https://docs.splunk.com/Documentation/Splunk/8.0.3/Knowledge/definecalcfields Calculated fields are fields that are created by performing calculations on existing fields using the eval command. Calculated fields can be used in the search bar to filter and transform events based on the calculated values. Calculated fields can also be based on an extracted field, which is a field that is extracted from raw data using various methods, such as regex, delimiters, lookups, etc. Calculated fields are not shortcuts for performing calculations using the eval command, but rather results of performing calculations using the eval command. Calculated fields can be applied to any field in Splunk, not only host and sourcetype.
Therefore, statements A, B, and D are true about calculated fields.

The Splunk Common Information Model (CIM) provides a methodology to normalize data from different sources and source types. The CIM defines a common set of fields and tags for different types of data, such as web, network, email, etc. This allows you to search and analyze data from different sources in a consistent way.

Explanation/Reference: https://docs.splunk.com/Documentation/Splunk/8.0.3/Knowledge/SetupaPOSTworkflowaction