Reference:
A calculated field is a field that you create based on the value of another field or fields1. You can use calculated fields to enrich your data with additional information or to transform your data into a more useful format1. Calculated fields can be based on extracted fields, which are fields that are extracted from your raw data using various methods such as regular expressions, delimiters, or key-value pairs1. Therefore, option B is correct, while options A, C and D are incorrect because tags, output fields for a lookup, and fields generated from a search string are not types of extracted fields.

The correct answer is C. A macro is a portion of a search that can be reused in multiple places.
A macro is a way to reuse a piece of SPL code in different searches. A macro can be any part of a search, such as an eval statement or a search term, and does not need to be a complete command. A macro can also take arguments, which are variables that can be replaced by different values when the macro is called. A macro can also contain another macro within it, which is called a nested macro1.
To create a macro, you need to define its name, definition, arguments, and description in the Settings > Advanced Search > Search Macros page in Splunk Web or in the macros.conf file. To use a macro in a search, you need to enclose the macro name in backtick characters (`) and provide values for the arguments if any1.
For example, if you have a macro named my_macro that takes one argument named object and has the following definition:
search sourcetype= object
You can use it in a search by writing:
my_macro(web)
This will expand the macro and run the following SPL code:
search sourcetype=web
The benefits of using macros are that they can simplify complex searches, reduce errors, improve readability, and promote consistency1.
The other options are not correct because they describe other types of knowledge objects in Splunk, not macros. These objects are:
A) An event type is a method of categorizing events based on a search. An event type assigns a label to events that match a specific search criteria. Event types can be used to filter and group events, create alerts, or generate reports2.
B) A field alias is a way to associate an additional (new) name with an existing field name. A field alias can be used to normalize fields from different sources that have different names but represent the same data. Field aliases can also be used to rename fields for clarity or convenience3.
D) An alert is a knowledge object that enables you to schedule searches for specific events and trigger actions when certain conditions are met. An alert can be used to monitor your data for anomalies, errors, or other patterns of interest and notify you or others when they occur4.
Reference:
About event types
About field aliases
About alerts
Define search macros in Settings
Use search macros in searches