The fields sidebar is a panel that shows the fields that are present in your search results2. The fields sidebar has two sections: selected fields and interesting fields2. Selected fields are fields that you choose to display in your search results by clicking on them in the fields sidebar or by using the fields command2. Interesting fields are fields that appear in at least 20 percent of events or have high variability among values2. For each field in the fields sidebar, you can select one of the following options: events with this field, rare values, top values by time or top values2. If you select rare values, Splunk will automatically pipe your search results to the rare command, which shows the least common values of a field2. Therefore, option B is correct, while options A, C and D are incorrect because they do not pipe your search results to the rare command.

The transaction command is a Splunk command that finds transactions based on events that meet various constraints .
Transactions are made up of the raw text (the _raw field) of each member, the time and date fields of the earliest member, as well as the union of all other fields of each member .
The transaction command groups events together by matching one or more fields that have the same value across the events . For example, | transaction clientip will group events that have the same value in the clientip field.

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The search command is used to filter or refine your search results based on a search string that matches the events2. The search command behaves exactly like search strings before the first pipe, which means that you can use the same syntax and operators as you would use in the initial part of your search2. Therefore, option D is correct, while options A, B and C are incorrect because they are not true statements about the search command.